Robinsons

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Robinsons

by RobertP » Wed Feb 03, 2016 9:14 am
Hello everyone,

The Robinsons have had three children of different ages. How old is the youngest today?

(1) The two older children have, together, 16 years
(2) The two younger children have, together, 9 years

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by GMATGuruNY » Wed Feb 03, 2016 9:24 am
RobertP wrote:Hello everyone,

The Robinsons have had three children of different ages. How old is the youngest today?

(1) The two older children have, together, 16 years
(2) The two younger children have, together, 9 years
Let:
y = the youngest child.
m = the middle child.
e = the eldest child.

Both statements are satisfied by the following cases:
y=4, m=5, e=11.
y=3, m=6, e=10.

Since y can be different values, the two statements combined are INSUFFICIENT.

The correct answer is E.
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by Matt@VeritasPrep » Mon Feb 08, 2016 9:20 am
I'd think of it this way:

a + b = 16
b + c = 9

So we have three variables but only two equations, so we're unlikely to be able to solve. (We could subtract the first equation from the second to find a - c = 7, or how MUCH older the oldest is than the youngest, but that isn't what we're asked to find, so no luck!)