Author 
Message 
TAGS:

Hide Tags

Intern
Joined: 05 Aug 2015
Posts: 46

Last year, sales at Company X were 10% greater in February than in Jan
[#permalink]
Show Tags
24 Apr 2016, 23:36
Question Stats:
70% (01:13) correct 30% (01:10) wrong based on 666 sessions
HideShow timer Statistics
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?
Official Answer and Stats are available only to registered users. Register/ Login.
_________________
Working towards 25 Kudos for the Gmatclub Exams  help meee I'm poooor




Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 8195
Location: Pune, India

Re: Last year, sales at Company X were 10% greater in February than in Jan
[#permalink]
Show Tags
28 Apr 2016, 21:41
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 (FebMarch) 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 AprilMay. 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)
_________________
Karishma Veritas Prep GMAT Instructor
Save up to $1,000 on GMAT prep through 8/20! Learn more here >
GMAT selfstudy has never been more personalized or more fun. Try ORION Free!




Intern
Joined: 03 Jul 2015
Posts: 5

Last year, sales at Company X were 10% greater in February than in Jan
[#permalink]
Show Tags
28 Apr 2016, 14:16
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




Board of Directors
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 3784
Location: India
GPA: 3.5
WE: Business Development (Commercial Banking)

Last year, sales at Company X were 10% greater in February than in Jan
[#permalink]
Show Tags
25 Apr 2016, 02:37
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? Find the missing link ( Much like Darwin's missing link ) 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..... AbhishekPS : 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)
_________________
Thanks and Regards
Abhishek....
PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS
How to use Search Function in GMAT Club  Rules for Posting in QA forum  Writing Mathematical Formulas Rules for Posting in VA forum  Request Expert's Reply ( VA Forum Only )



Intern
Joined: 11 Aug 2014
Posts: 10
Location: United States
Concentration: International Business, Entrepreneurship
GPA: 3.9

Re: Last year, sales at Company X were 10% greater in February than in Jan
[#permalink]
Show Tags
21 Jul 2016, 04:35
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 (FebMarch) 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 AprilMay. 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) 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)



Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 8195
Location: Pune, India

Re: Last year, sales at Company X were 10% greater in February than in Jan
[#permalink]
Show Tags
21 Jul 2016, 21:17
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 (FebMarch) 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 AprilMay. 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) 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.
_________________
Karishma Veritas Prep GMAT Instructor
Save up to $1,000 on GMAT prep through 8/20! Learn more here >
GMAT selfstudy has never been more personalized or more fun. Try ORION Free!



Intern
Joined: 06 Apr 2017
Posts: 29
Location: United States (OR)
Concentration: Finance, Leadership
GMAT 1: 730 Q48 V44 GMAT 2: 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]
Show Tags
03 Aug 2017, 10:16
All of the increases and decreases can be represented in base10, so pick a fairly large number that's base10 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 base10. You should know shortcuts for these operations, or GMAT estimation questions will frustrate you and devour the clock.
Answer D



Intern
Joined: 29 May 2017
Posts: 17

Re: Last year, sales at Company X were 10% greater in February than in Jan
[#permalink]
Show Tags
01 Sep 2017, 18:49
Let the sales is May is 100. Then June sell = 100+5=105 April sell=100+10=110 March sell=11020=90 Feb sell=90+15=105 Jan sell=10515=90. Hence, January sell is near to May sell.



EMPOWERgmat Instructor
Status: GMAT Assassin/CoFounder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 12196
Location: United States (CA)

Re: Last year, sales at Company X were 10% greater in February than in Jan
[#permalink]
Show Tags
21 Jan 2018, 13:10
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. Final Answer: GMAT assassins aren't born, they're made, Rich
_________________
760+: Learn What GMAT Assassins Do to Score at the Highest Levels Contact Rich at: Rich.C@empowergmat.com
Rich Cohen
CoFounder & GMAT Assassin
Special Offer: Save $75 + GMAT Club Tests Free
Official GMAT Exam Packs + 70 Pt. Improvement Guarantee www.empowergmat.com/
***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************



Intern
Joined: 14 Jul 2017
Posts: 15

Re: Last year, sales at Company X were 10% greater in February than in Jan
[#permalink]
Show Tags
24 Mar 2018, 08:41
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: 7

Re: Last year, sales at Company X were 10% greater in February than in Jan
[#permalink]
Show Tags
04 Apr 2018, 19:03
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: 91
Location: Canada
WE: Consulting (Other)

Re: Last year, sales at Company X were 10% greater in February than in Jan
[#permalink]
Show Tags
03 Jun 2018, 14:43
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 (FebMarch) 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 AprilMay. 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.
_________________
Migatte no Gokui




Re: Last year, sales at Company X were 10% greater in February than in Jan &nbs
[#permalink]
03 Jun 2018, 14:43






