Alexander D. answered • 03/14/19

Quantitative GRE Tutor

Your reasoning is only slightly incorrect. The issue is that you're not constrained to choose 2 biographies, but rather **at least 2**. This means you can also choose 3 biographies or 4. So, the number of outcomes is:

4 Biographies: 4 C 4 = 1

3 Biographies, 1 novel: 4 C 3 * 6 C 1 = 24

2 Biographies, 2 novels: 4 C 2 * 6 C 2 = 6 * 15 = 90

So, the total options are 90 + 24 + 1 = 115.

Notice how that's very close to your answer: 4 C 2 * 8 C 2 = 112.