Last visit was: 14 Jun 2024, 02:56 It is currently 14 Jun 2024, 02:56
Toolkit
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

# Last year, sales at Company X were 10% greater in February than in Jan

SORT BY:
Tags:
Show Tags
Hide Tags
Intern
Joined: 05 Aug 2015
Posts: 31
Own Kudos [?]: 357 [173]
Given Kudos: 36
Tutor
Joined: 16 Oct 2010
Posts: 14950
Own Kudos [?]: 65900 [84]
Given Kudos: 433
Location: Pune, India
Intern
Joined: 03 Jul 2015
Posts: 5
Own Kudos [?]: 66 [65]
Given Kudos: 13
General Discussion
Board of Directors
Joined: 11 Jun 2011
Status:QA & VA Forum Moderator
Posts: 6065
Own Kudos [?]: 4738 [4]
Given Kudos: 463
Location: India
GPA: 3.5
Last year, sales at Company X were 10% greater in February than in Jan [#permalink]
3
Kudos
1
Bookmarks
happyface101 wrote:
Last year, sales at Company X were 10% greater in February than in January, 15% less in March than in Feb, 20% greater in April than in March, 10% less in May than in April, and 5% greater in June than in May. In which month were sales closest to Jan?

a. Feb
b. Mar
c. Apr
d. May
e. June

What's the easiest / quickest way to solve this?

Quote:
10% greater in February than in January
15% less in March than in Feb
20% greater in April than in March
10% less in May than in April
5% greater in June than in May

Can you find the link ? Yes you are correct, sales of next month depends on the sale of This month............

So, Assume Sales in Jan as 1000 or x as you wish and proceed.....

Abhishek

PS : This is a calculation intensive Problem and will result in decimal numbers so, it will be better to assume the sales figure of Jan as X and solve algebraically ( My personal Opinion)
Intern
Joined: 11 Aug 2014
Posts: 7
Own Kudos [?]: 3 [1]
Given Kudos: 82
Location: United States
Schools: HBS '18
GPA: 3.9
Re: Last year, sales at Company X were 10% greater in February than in Jan [#permalink]
1
Kudos
VeritasPrepKarishma wrote:
happyface101 wrote:
Last year, sales at Company X were 10% greater in February than in January, 15% less in March than in Feb, 20% greater in April than in March, 10% less in May than in April, and 5% greater in June than in May. In which month were sales closest to Jan?

a. Feb
b. Mar
c. Apr
d. May
e. June

What's the easiest / quickest way to solve this?

You can do this question easily if you understand number properties. Let me try to explain. Note that explaining takes quite a bit of time though if you understand this, thinking through doesn't take more than a few seconds:

There is an increase, then a decrease, then an increase, then a decrease and an increase again.
Most probably, when you apply an increase and then a decrease, the figure will come back close to its original value. So March or May are the best bets.

The first iteration (Feb-March) will take it much lower since after you increase by 10%, you are decreasing by a number greater than 10%. Actually, to come back to original, you need to decrease by a number slightly smaller than 10%.
Take an example: original value = 100
Increase by 10% to get 110.
Now if you decrease it by about 9%, you will get 100 back. But you actually decrease by 15% so it goes down. So March is unlikely.

Next iteration is April-May. You increase a number smaller than 100 by 20% and then bring it down by 10%. This should be the answer in all probability. Though 20% seems like a big increase compared to the 10% decrease so it looks like the figure might be much greater than original but the next step (5% increase) is a further increase so June is anyway not possible.
Just to be sure, let's see the effect of these 4 operations on the original value:
(11/10)*(17/20)*(6/5)*(9/10) = (99/100)*(102/100) (club together first and last terms to get 99/100 and second and third terms to get 102/100)
This would be extremely close to 1.

Why do we club 2nd and 3rd ?

(11/10)*(17/20)*(6/5)*(9/10) = (99/100)*(102/100) (club together first and last terms to get 99/100 and second and third terms to get 102/100)
Tutor
Joined: 16 Oct 2010
Posts: 14950
Own Kudos [?]: 65900 [3]
Given Kudos: 433
Location: Pune, India
Re: Last year, sales at Company X were 10% greater in February than in Jan [#permalink]
2
Kudos
1
Bookmarks
parvgugnani wrote:
VeritasPrepKarishma wrote:
happyface101 wrote:
Last year, sales at Company X were 10% greater in February than in January, 15% less in March than in Feb, 20% greater in April than in March, 10% less in May than in April, and 5% greater in June than in May. In which month were sales closest to Jan?

a. Feb
b. Mar
c. Apr
d. May
e. June

What's the easiest / quickest way to solve this?

You can do this question easily if you understand number properties. Let me try to explain. Note that explaining takes quite a bit of time though if you understand this, thinking through doesn't take more than a few seconds:

There is an increase, then a decrease, then an increase, then a decrease and an increase again.
Most probably, when you apply an increase and then a decrease, the figure will come back close to its original value. So March or May are the best bets.

The first iteration (Feb-March) will take it much lower since after you increase by 10%, you are decreasing by a number greater than 10%. Actually, to come back to original, you need to decrease by a number slightly smaller than 10%.
Take an example: original value = 100
Increase by 10% to get 110.
Now if you decrease it by about 9%, you will get 100 back. But you actually decrease by 15% so it goes down. So March is unlikely.

Next iteration is April-May. You increase a number smaller than 100 by 20% and then bring it down by 10%. This should be the answer in all probability. Though 20% seems like a big increase compared to the 10% decrease so it looks like the figure might be much greater than original but the next step (5% increase) is a further increase so June is anyway not possible.
Just to be sure, let's see the effect of these 4 operations on the original value:
(11/10)*(17/20)*(6/5)*(9/10) = (99/100)*(102/100) (club together first and last terms to get 99/100 and second and third terms to get 102/100)
This would be extremely close to 1.

Why do we club 2nd and 3rd ?

(11/10)*(17/20)*(6/5)*(9/10) = (99/100)*(102/100) (club together first and last terms to get 99/100 and second and third terms to get 102/100)

You don't have to - you can to help you in your calculation. The denominators multiply to give 100. The numerator is something very close to 100. So you know that by clubbing, you can easily approximate.
Intern
Joined: 06 Apr 2017
Posts: 21
Own Kudos [?]: 104 [15]
Given Kudos: 38
Location: United States (OR)
GMAT 1: 730 Q49 V40
GPA: 3.98
WE:Corporate Finance (Health Care)
Re: Last year, sales at Company X were 10% greater in February than in Jan [#permalink]
12
Kudos
3
Bookmarks
All of the increases and decreases can be represented in base-10, so pick a fairly large number that's base-10 and work through the calculations.

$$January=10,000$$
$$February=10,000*1.1 = 11,000$$
$$March=11,000 *.85 = 10,000*.85 + 1,000*.85=8,500 + 850 =9,350$$
$$April=9,350*1.2=9,350+.2*9,350=9,350+1,870=11,220$$
$$May=11,220*.9=11,220-.1*11,220=11,220-1,122=10,098$$

Don't calculate June - obviously, if $$10,098$$ gets larger, then it's farther from $$10,000$$ than May. The important piece here is being able to quickly do calculations with numbers in base-10. You should know shortcuts for these operations, or GMAT estimation questions will frustrate you and devour the clock.

Intern
Joined: 29 May 2017
Posts: 11
Own Kudos [?]: 2 [1]
Given Kudos: 22
Re: Last year, sales at Company X were 10% greater in February than in Jan [#permalink]
1
Kudos
Let the sales is May is 100.
Then June sell = 100+5=105
April sell=100+10=110
March sell=110-20=90
Feb sell=90+15=105
Jan sell=105-15=90.
Hence, January sell is near to May sell.
GMAT Club Legend
Joined: 19 Dec 2014
Status:GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Posts: 21843
Own Kudos [?]: 11720 [2]
Given Kudos: 450
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Re: Last year, sales at Company X were 10% greater in February than in Jan [#permalink]
1
Kudos
1
Bookmarks
Hi All,

TESTing VALUES (the approach used by a number of the posters in this thread) works perfectly in these types questions. You can also approach these types of questions algebraically (you just have to be careful with the 'math work').

January = X dollars in sales
February = 1.1X dollars in sales
March = 1.1X - (.15)(1.1X) = 1.1X - .165X = .935X dollars in sales
April = .935X + (.2)(.935X) = 1.122X dollars in sales
May = 1.122X - (.1)(1.122X) = 1.0098X dollars in sales
June = 1.0098X + .(.05)(1.0098X) = clearly more than the dollar sales in May

We're asked for the month that was closest to January in sales (so closer to X). That is clearly May.

Looking at this work, you should be able to see how TESTing VALUES is an easier approach.

GMAT assassins aren't born, they're made,
Rich
Intern
Joined: 14 Jul 2017
Posts: 22
Own Kudos [?]: 2 [1]
Given Kudos: 215
Re: Last year, sales at Company X were 10% greater in February than in Jan [#permalink]
1
Kudos
For me it was easier to solve using 1$as the sales amount for jan 10% greater in February than in January ---> Feb = 1.1x1 =1.1 15% less in March than in Feb ---> Mar = 1.1x0.85=0.93 20% greater in April than in March ---> Apr = 0.93x1.2=1.12 10% less in May than in April ---> May = 1.12x0.9=1.004 5% greater in June than in May --->Jun = 1.0x1.05=1.05 Hence, May is the closest. Intern Joined: 04 Feb 2018 Posts: 6 Own Kudos [?]: 5 [3] Given Kudos: 24 Re: Last year, sales at Company X were 10% greater in February than in Jan [#permalink] 2 Kudos 1 Bookmarks If you look at the % changes, you can see that the 15% is the trickiest one to handle. Try to choose a number that can handle that easily. Jan, Feb (+10%), Mar (-15%), Apr (+20%), May (-10%), Jun (+5%) Let's choose Mar = 85, then: * Feb = 100, Jan = ~90 * Apr = 102, May = ~90, Jun =~95 Pretty clear that Jan and May are the closest. Manager Joined: 20 Jan 2016 Posts: 56 Own Kudos [?]: 61 [0] Given Kudos: 68 Location: Canada Schools: HBS '18 WE:Consulting (Other) Re: Last year, sales at Company X were 10% greater in February than in Jan [#permalink] VeritasPrepKarishma wrote: happyface101 wrote: Last year, sales at Company X were 10% greater in February than in January, 15% less in March than in Feb, 20% greater in April than in March, 10% less in May than in April, and 5% greater in June than in May. In which month were sales closest to Jan? a. Feb b. Mar c. Apr d. May e. June What's the easiest / quickest way to solve this? You can do this question easily if you understand number properties. Let me try to explain. Note that explaining takes quite a bit of time though if you understand this, thinking through doesn't take more than a few seconds: There is an increase, then a decrease, then an increase, then a decrease and an increase again. Most probably, when you apply an increase and then a decrease, the figure will come back close to its original value. So March or May are the best bets. The first iteration (Feb-March) will take it much lower since after you increase by 10%, you are decreasing by a number greater than 10%. Actually, to come back to original, you need to decrease by a number slightly smaller than 10%. Take an example: original value = 100 Increase by 10% to get 110. Now if you decrease it by about 9%, you will get 100 back. But you actually decrease by 15% so it goes down. So March is unlikely. Next iteration is April-May. You increase a number smaller than 100 by 20% and then bring it down by 10%. This should be the answer in all probability. Though 20% seems like a big increase compared to the 10% decrease so it looks like the figure might be much greater than original but the next step (5% increase) is a further increase so June is anyway not possible. Just to be sure, let's see the effect of these 4 operations on the original value: (11/10)*(17/20)*(6/5)*(9/10) = (99/100)*(102/100) (club together first and last terms to get 99/100 and second and third terms to get 102/100) This would be extremely close to 1. So answer would be May. Answer (D) This is genius and right off the bat narrows it down to 2 choices (since There is an increase, then a decrease, then an increase, then a decrease and an increase again). The logic makes perfect sense. If one is under time pressure, this is a much more efficient approach then using algebra or picking 'smart' numbers which are time consuming to calculate in this case. VP Joined: 14 Feb 2017 Posts: 1109 Own Kudos [?]: 2177 [0] Given Kudos: 368 Location: Australia Concentration: Technology, Strategy GMAT 1: 560 Q41 V26 GMAT 2: 550 Q43 V23 GMAT 3: 650 Q47 V33 GMAT 4: 650 Q44 V36 GMAT 5: 600 Q38 V35 GMAT 6: 710 Q47 V41 WE:Management Consulting (Consulting) Re: Last year, sales at Company X were 10% greater in February than in Jan [#permalink] I solved this by plugging-in$1000, but I agree it's fairly calculation intensive and there is a greater chance of error under pressue.

so you just took the percentage fluctuations 11/10 * 85/100 * 6/5 * 9/10 to indicate that after the affect of May's percentage change, the net movement is 99/100 *102/100 - a number close to 1, thus May is correct since a further increase would obviously deviate from how close May is from 1 and thus from its original value
Intern
Joined: 18 Jun 2019
Posts: 12
Own Kudos [?]: 60 [8]
Given Kudos: 206
Re: Last year, sales at Company X were 10% greater in February than in Jan [#permalink]
5
Kudos
3
Bookmarks
This is a problem of successive percentage change
So if there is a percentage change by a% and then by b%, resultant % change is given by formula-

Resultant % change = a + b + $$\frac{( a * b )}{100}$$

For Feb ;
Resultant % change = 10 % ---- (Given)

Till Mar ; (15% less)
Resultant % change = 10 + (-15) + $$\frac{(10 * (-15))}{100}$$ = -6.5%
Similarly,

Till Apr ; (20% greater)
Resultant % change = -6.5 + 20 + $$\frac{((-6.5) * 20)}{100}$$ = 13.5 - 1.3 ~ 12 %

Till May ; (10% less)
Resultant % change = 12 + (-10) + $$\frac{(12 * (-10))}{100}$$ = 0.8 %

Till Jun ; (5% greater)
Resultant % change = 0.8 + 5 + $$\frac{(0.8 * 5)}{100}$$ = 6.xx %

So , Least change is in May (0.8%) ... Ans : D
Intern
Joined: 26 May 2019
Posts: 30
Own Kudos [?]: 39 [5]
Given Kudos: 249
Re: Last year, sales at Company X were 10% greater in February than in Jan [#permalink]
3
Kudos
2
Bookmarks
I answered this correctly during my practice exam, but it was very time consuming so I wanted to test what was the best and fastest way to solve this.

After testing out all of these methods posted previously here, I found the fastest explanation for me was from VeritasKarishma from a concept standpoint. However I also realized that simple number testing is especially effective for this problem because all of the percentage changes are multiples of 5, so the numbers can be quickly calculated by plugging values for 10% or 5%. Being under a time crunch and with wanting to see numbers to verify under pressure while testing this may be very effective for people without needing to deal with a lot of successive percentage change fractions.

To illustrate:

Let January = $100 February is 10% greater --> 10% of$100 is $10 so this =$110
March is 15% less --> 15% is 10% + 5%. So 10% of $110 is$11, and half of that is approx. $6. so$110 - $11 -$6 = $93 April is 20% greater --> 10% of$93 is approx. $9, so 20% is$18, so $93 +$18 = $111 May is 10% less --> THIS IS WHERE IT CLICKS! 10% of$111 is $11.$111 - $11 =$100
We could continue a step further to May which is 5% greater, but we can already quickly tell then that it would be $105, and therefore May is the closest to January. Answer D GMAT Club Legend Joined: 03 Oct 2013 Affiliations: CrackVerbal Posts: 4940 Own Kudos [?]: 7732 [1] Given Kudos: 216 Location: India Re: Last year, sales at Company X were 10% greater in February than in Jan [#permalink] 1 Kudos Top Contributor Last year, sales at Company X were 10% greater in February than in January, 15% less in March than in Feb, 20% greater in April than in March, 10% less in May than in April, and 5% greater in June than in May. In which month were sales closest to Jan? a. Feb b. Mar c. Apr d. May e. June If you know the basics of the Percentage less/more and the 10 % base rule, you can easily tackle this question in less than 2 mins. When you analyze the percentages used here i.e 10%, 15 %,20%, and 5 %. They are very easy to calculate by using the 10 % percent base method. For those who don't know what is 10 percent base method is, let me give you a brief. 10 % of No = $$\frac{10}{100}$$* No = $$\frac{No}{10}$$. So 10 % of any number is very easy to find, i.e you need to divide the number by 10. For eg. 10 % of 450 = 45 ---> Divide 450/10 10 % of 45 = 4.5 ---> Divide 45/10 By using 10 % as the base, you can calculate other percentages as well. 20 % of a No = 10 % of No * 2 5 % of a No = 10 % of No / 2 15 % of a No = 10 % of No + 5 % of No So practice and try to do these calculations in mind. It will help you in saving time. Just an overview of % less/more, before going forward to the explanation . X is 10 % less than Y i.e X= Y - 10 % of Y or X = 90% of Y Similarly, If X is 10 % more than Y i.e X = Y + 10 % of Y or X = 110 % of Y Here, in this question, let's try to apply both concepts we just learned. Assume that the sales in Jan be 100. Now, we are going to find the sales in each month as per the data given here and find which month's sales will be close to Jan. a. Feb The sales at Company X were 10% greater in February than in January. Sales in Feb = Sales in Jan + 10 % of Sales in Jan = 100 + 10 = 110. You can blindly eliminate this option as it's clearly given that sales in Feb are 10 % greater than in Jan. So it's nowhere close to Jan b. Mar The sales at Company X were 15% less in March than in Feb. Sales in March = Sales in Feb - 15 % of sales in Feb = 110 - 15 % of 110= 110 - 16.5 = 94.5 Since 94.5 is not close to 100, you can eliminate this option. Also if you analyze logically, March won't be the correct answer because 10 % increase and 15 % decrease successively will not get back to the original value ( 0% change ) c. Apr The sales at Company X were 20% greater in April than in March. Sales in April= Sales in March + 20 % of sales in March = 94.5 + 20 % of 94.5 = 94.5 + 19 = 113.5 Note: You can use the 10 % percent base method to find 20 % of 94.5. 10% of 94.5 = 9.45 20 % of 94.5 = 9.45 * 2 ~ 19 We don't need to find the exact value here. An approximate value will serve our purpose as we are comparing the sales. 113.5 is way greater than 100, So we can eliminate Option C as well. d. May The sales at Company X were 10% less in May than in April. Sales in May = Sales in April - 10 % of Sales in April = 113.5 - 11.35 = ~ 102 Which is very close to 100 i.e sales in month of Jan e. June The sales at Company X were 5% greater in June than in May. We can eliminate option E as sales in June is 5 % more than in May (~102 ). So it definitely won't be close to 100. Option D, May is the correct answer as it's very close to 100 i.e Jan sales. Thanks, Clifin J Francis, GMAT QUANT SME Intern Joined: 28 Apr 2023 Posts: 6 Own Kudos [?]: 0 [0] Given Kudos: 0 Re: Last year, sales at Company X were 10% greater in February than in Jan [#permalink] karim2982 wrote: This can be solved using smart numbers: Let January =$100. (Keep in mind we are using "approximate" values, as per the problem). We have:
Jan = $100 10% greater in February than in January ---> Feb = 1.1 Jan =$110
15% less in March than in Feb ---> Mar = 0.85 Feb = $93.5 20% greater in April than in March ---> Apr = 1.2 Mar =$112
10% less in May than in April ---> May = 0.9 Apr = $101 (we have a winner) 5% greater in June than in May --->Jun = 1.05 May =$106

Ans D

this still requires quite a bit of math.

is there a shorter way? with multiple estimations? It would take me 20 minutes to do it this way
Re: Last year, sales at Company X were 10% greater in February than in Jan [#permalink]
Moderator:
Math Expert
93707 posts