A test maker is to design a probability test from a list of

Question

A test maker is to design a probability test from a list of 21 questions. The 21 questions are classified into three categories: hard, intermediate and easy. If there are 7 questions in each category and the test maker is to select two questions from each category, how many different combinations of questions can the test maker put on the test?
A) 3*(7!/(5!2!))
B) 3*(7!/(5!))
C) 3*(7!/(2!))
D) 3*21
E) 72

A) 3*(7!/(5!2!)) 
B) 3*(7!/(5!)) 
C) 3*(7!/(2!)) 
D) 3*21 
E) 72

Bunuel · Answer

There is no correct choice!

The number of combinations will be C(2,7)*C(2,7)*C(2,7)=C(2,7)^3=21^3=9261

Check the source. A and C give the same answers.

mendelay · Answer

The question is from PlatinumGmat https://www.platinumgmat.com/practice_gm ... on_id=2252
and the OA given there is A.

However, I disagree because 7C2*7C2*7C2 ≠ 37C2.
I think the answer is none of the above.

Bunuel · Answer

They made a mistake: 7C2*7C2*7C2 ≠ 37C2 its (7C2)^3=9261. There must be a typo.

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A test maker is to design a probability test from a list of

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