Brent@GMATPrepNow wrote:

btg_13423 wrote:
If the average age of three people is 21 years, is the youngest older than 13?

(1) The oldest is 25.
(2) One person is 24.

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How's this . . .

Target question: Is the youngest older than 13?

Given: The average age of three people is 21 years
If the average (arithmetic mean) the 3 ages is is 21, then the SUM of all 3 ages must = (3)(21) = 63
If we let A, B and C be the ages, in ascending order, then A + B + C = 63

Statement 1: The oldest is 25
So, C = 25
This means that A + B + 25 = 63
In other words, A + B = 38
Let's see what happens if we minimize the value of A.
To MINIMIZE the value of A, we must MAXIMIZE the value of B.
Since 25 is the greatest age, we know that B < 25
So, the MAXIMUM value of B is 24, in which case the MINIMUM value of C is 14 (since A + B = 38).
In other words, C must be greater than or equal to 14
So, the youngest person is definitely older than 13
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: One person is 24
Consider these 2 possible cases:
case a: the ages are 3, 24, 36 in which case the youngest person is NOT older than 13
case b: the ages are 14, 24, 25 in which case the youngest person IS older than 13
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Answer = A

Cheers,
Brent

Brent@GMATPrepNow wrote:

Uva@90 wrote: I have doubt with Answer A,
This question is of type Yes/No

Coming to statement 1:
We know that, A+B = 38
We also know that Oldest age is 25.

So, We can split into 13+25 =38
(In Question No-where it is mentioned that all the three people have different ages. Even two could have same age right.)
Now answer is NO. Youngest age is not greater than 13

Or

14+24
Here answer is Yes. Youngest age is greater than 13

Hence Statement 1 is Insufficient na ?

Could you please explain me where I went wrong.

Thanks in advance.
Regards,
Uva.

Hi Uva,

I had my doubts about this question as well.

You're right in that the question doesn't state that the 3 ages are different. However, if we say that the oldest is 25 years old, then the singular word "is" suggests that there is only one oldest person, which means the other 2 people must be younger than 25.

For example, if the ages were 13, 25 and 25, would we say "the oldest IS 25?"

Cheers,
Brent