scbguy wrote:

I was doing percentages and this is a percentage question highlighted in

mgmat strategy book but in the

og they have done it through algebra

How can we do it percentage wise

Marys income is 60 percent more than tims income and tims income is 40 percent less than juans income. What percentage of juans income is marts income

A) 124%

b) 120 %

c) 96 %

d) 80 %

e) 64 %

I solved it like this

Keep tims income as 100 hence marys income is 160 and juans is 140 so effectively it will be 160/140x 100 which is approximate 96%

But that's wrong the answer is c

The error in your solution is that Tim's income is 40% less than Juan's. Juan's income is not 40% more than Tim's. These are 2 different things. Say I scored a 90 in an exam and you scored a 100. My score is 10%

less than yours [10% = (90 - 100)/100] Notice that your score, 100, is the base on which we are comparing. On the other hand, your score is 11.11%

more than mine. Now my score is the base on which we are comparing [11.11% = (100 - 90)/90]

The trick is to assign 100 for easy calculations but to assign it to the 'right' person. Assign 100 to the person who is the base (which means the person to whom everyone else links up) e.g.

Mary's income is 60% more Than Tim's income

- Mary's income is linked to Tim's. So, I might assign 100 to Tim if there is no Juan.

and Tim's income is 40% less than juan's income.

- Now Tim's income is further linked to Juan. Juan's income is the base against which others are compared.

So I assign 100 to Juan. Calculations will not be tough in this case. Else they could get a little tricky.

Juan - 100

Tim - 60

Mary - 96

So Mary's income is 96% of Juan's income (which is 100).

_________________

Karishma

Veritas Prep | GMAT Instructor

My Blog

Get started with Veritas Prep GMAT On Demand for $199

Veritas Prep Reviews