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
_________________