Mistake in PrepSwift Quant Tickbox Quiz #14 - question 17?

GRE Quant Problem Solving
1

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In this question, can anyone check with N=2. in my calculations, it doesn’t work.
if we take n=2 then total 5 books - 3 novels and 2 biographies.
now it can be - NBNBN (so basically Novels can arrange themselves in 3 positions in 3! ways and biographies can arrange themselves in 2 positions in 2! ways so total 3!*2! ways i.e., 12 ways total.

now options -
A - incorrect
B - 2(n^2 + n) it works with n=2 we get 12
C - n(n+1)! it also works with n=2 we get 12
D - (n!)^2(n+1) - it also works with n=2 we get 12
E - incorrect
how can we get 3 correct answers when taking n=2?
there is also no condition that specifies that we cannot take N=2
can someone please check this question?

2

What about if n = 3?

4

Greg uses n=3 in the explanation but a correct answer should work for ALL values of n and not just some random values so I do not think this question makes sense.

5

Option D has to work for all values of n. The other options won’t.

6

yes in exam environment you cannot do this trial and error. there is only one correct answer for all options.

7

You’re doing this with choosing numbers, not algebraically. And it is very normal to do “trial and error” with choosing numbers. The goal with this strategy is to incrementally eliminate incorrect options - which you did in your above solution by removing options A and E.