How many people chose A?

In a survey people had to choose either A, B, C or D.

The percentage of people that chose B, C and D are shown here:

B- 25% 

C- 35%

D- 30%

You are also told that 150 people chose B. How many chose A?

So first of all lets see what percentage of people chose A. We know that all the %s must add up to 100, so the percentage of people who chose A can be worked out by:

100 - (25 + 35 + 30) = 100 - 90 = 10

So 10% of people chose A. 

Now lets look at how many people 10% is, we know that 150 people chose B, and so 25% of the sample is 150 people. So there must have been 150 x 4 = 600 people who answered the survey as 25% x 4 = 100%.

So now we work out 10% of 600, which equals 60.

So, 60 people chose A.