Three boys have ages 2, 4, and 5, while three… | GMAT Sprint

Free Practice Question

PS · Problem Solving

705-805

Probability

Three boys have ages 2, 4, and 5, while three girls have ages 3, 6, and 7. If two boys and two girls are randomly selected, and the sum of their ages is z, what is the difference between the probability that z is even and the probability that z is odd?

Answer Choices

Correct answer marked below

1/9

Correct

1/6

2/9

1/4

1/2

See the full step-by-step explanation

You can see the correct answer above. Sign in for free to unlock the complete worked solution.

Track your performance and improve

Get detailed analytics, unlock full explanations, and move up difficulty tiers as you practice.

Start for free Sign in

Explanation

Preview

Official Explanation

Official

Boys' age pairs:

2+4=6

(even),

2+5=7

(odd),

4+5=9

(odd). Girls' age pairs:

3+6=9

(odd),

3+7=10

(even),

6+7=13

(odd). Combining each pair: 6+9=15 (odd), 6+10=16…

Read the full explanation

Create free account Sign in

Comments

No comments yet

Be the first to share your thoughts and help others understand it better.

What this question tests

What it tests

Your ability to compute probabilities of single and compound events, including 'at least one' questions.

Common trap

Forgetting to use the complement for 'at least one', or treating dependent events as independent.