Each person in a certain group supports only one of two candidates R and T. Of the people in the group, 45 percent support Candidate R and the rest support Candidate T. How many people in the group are in favor of a flat tax ?

(1) Of the people in the group who support Candidate R, 58 percent are in favor of flat tax

(2) Of the people in the group who support Candidate T, 22 are in favor of a flat tax.

Here's my working for this problem:

Lets assume no. of people in group = 100.
R supporters = 45 (45% of 100)
T supporters = 55 (55% ("the rest" of 100)

(1) 58% of 45 -> INSUFF ... as this only gives us number of people in favor of flat tax from the group supporting candidate R. We also need to know how many of candidate T's supporters are in favor of flat tax, to determine how many people in the group are in favor of flat tax.

(2) Of the people in the group supporting Candidate T (55) ... 22 are in favour of flat tax. -> INSUFF ... this doesnt give us information about Candidate R's supporters.

(1) and (2) ... we have both candidate R's flat tax supporters (58% of 45), and candidate T's flat tax supporters (22), and hence the total number of people in the group in favor of a flat tax is (0.58*45) + 22. SUFF

So my working points to the answer as being C.

However the this is coming out as incorrect. WHY? where am I going wrong here ? I suspect I am making a simple mistake and falling into a trap somewhere.

Thanks in advance

Hi folks ... ignore my last question. I have found the "simple" mistake I was making ! I shouldnt have plugged in numbers !

(1) Of the people in the group who support Candidate R, 58 percent are in favor of flat tax

We dont know exactly how many people are supporting R. We only know it is 45% of a x (where x is the number of people in the group).

So this means the answer is E.

Thanks.

sounds like you're on your way. if you have any other questions about this problem, feel free to post them.

Hello,

That's how GMAT forces every test taker to concentrate fully.

BR

abedinbhuiyan

Good point abedinbhuiyan.

Thanks all!

_________________
Jamie Nelson
ManhattanGMAT Instructor

Why is it that you cannot pick 100 as a number for the total?

Thanks

Hi taniafconca,

In a situation like this, you can not pick an arbitrary number (like picking the 100) to 'prove a positive', that is a particular answer. That is because if a statement is true in a situation like this it must be true (and the same answer) for ALL numbers you pick for an example. Try the number 200, you still get sufficient for that particular number but the answer is different, so the true answer is 'not sufficient'. Even if it were true for a 100 numbers you still would not have proved it was true for ALL numbers. You can see from this that you also need to know something about the total number of people before you can answer the question.

BTW: The reason people do use examples to work things out is that you only need one example where the results are insufficient to show that is not true for ALL numbers because you just demonstrated it was not true for that number.

because the question says “how many”, not “what proportion” or “what percentage”.

let's say that ten percent of the population of some town is below the poverty line. how many people in that town are below the poverty line? we clearly can't say without having a figure for the population of the town. (in the same example, you can probably also see the illogic of fixing a total of 100.)