Try number stratergy on this problem

GRE Quant Problem Solving
1

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this is manhattan’s question. I tried number stratergy, but inly a specific combination had worked.
I tried [1,3,0] (in the order Joan’s age, Kylie,Lillian) . it yielded me a total of 4 and thus the one which gets divided by 4 works and thus, 52 is the answer.

But i tried anther combination (2,4,1), which yielded 7, none of the answers are divisible by 7. Where did i go wrong here?

2

I don’t think someone can celebrate their birthday when their age is 0…

Anyway, let J, K and L be the ages of the 3 people. Then, we know that J + 2 = K and K = L + 3. Then, J + K + L = (K - 2 + K + L) = (L + 3 - 2 + L + 3 + L) = (3L + 4). In other words, when divided by 3, we have remainder 1. Only 52 satisfies the criteria.

3

Hey, thanks for the reply. I was aware of this , but my doubt is why did the combination (2,4,1) not work? i Chose the numbers as dictated by the problem, so naturally it should work, but it didn’t. That’s my main puzzle.

4

Because that’s simply not part of the options. It’s not wrong per se, but that’s not the option amongst the five. If 7 was part of the options, it would be correct to select that.

5

yeah , but if we take the first case (1,3,0) , the sum is 4 . Even though there was no 4 in the answer, i thought , maybe a multiple that of 4 that would satisfy the requirements work (just like ratio problems). And 52 was there. But the same case did not work for (2,4,1). No multiple of 7 had been there in the options

6

That is faulty reasoning, and you were simply lucky this time. The same reason

failed.

7

Got it thanks !