Source: Official Guide for GMAT Review 2016 Problem Solving; #11

1

# If it is assumed that 60 percent of

If it is assumed that 60 percent of those who receive a questionnaire by mail will respond and 300 responses are needed, what is the minimum number of questionnaires that should be mailed?

### 3 Explanations

1

John Robertson

Idea: Percentages, simplify fractions before solving
Find: 60% of X IOT equal needed 300 responses, from X total
(60/100)x=300
(6/10)x=300
(3/5)x=300
x/5=100 ....(I divided by 3 first bc 300/3 is quicker than 300x5 i think, and gets you to a simple 100xZ multiplication)
x=100*5=500, D

Dec 17, 2016 • Comment

Cydney Seigerman, Magoosh Tutor

Nice work, John! For this problem, we can find the number of questionnaires to send by finding for what number x, 60% = 300, the number of desired responses. Also, excellent job simplifying the calculation to do it in the most efficient way possible for you :) Thanks for sharing your solution!

1

Sunita Dutta

I think, we can do the same using the basic method of calculating percentage. 60% of what will give 300, i,e. 60/100 of x =300 which gives x=500

Sep 28, 2016 • Comment

Cydney Seigerman, Magoosh Tutor

Yes, this is another way to solve this question and a very efficient way to arrive at the correct solution. Great job! And thanks for sharing your solution :)

2

Osvaldo Hernandez

For this question I followed a very basic approach to solving it, as I have been out of practice for awhile, but still managed to get the right answer by multiplying by 10% and adding it.

First, I just went down the answer choices and divided them in half (50%). Then I would add the remaining 10% to that answer choice I cut in half that I got from keeping in mind that 10% of 100 is 10 to help me get a ball park idea.

a) 200 + 40 (40 is 10% of 400) = 240
b)210 +42= 252
c) 240 + 48= 288
d)250 + 50=300
e)300+ 60= 360
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