OG #11 - combination

What is the best way to approach this question? I have a hard time organizing combination questions.

Seems to be ETS material, but clearly not the Big Book.

Notice that there are many ways we can satisfy the 10 books requirement - for instance 2 bio and 8 novels, 3 bio and 7 novels and 4 bio/6 novels. Consider each case separately and add them up.

umm you post twice
2+ biographies is the key information here, so we have 3 cases 4C2*6C2+4C3*6C1+4C4*6C0=115

Thank you. Sorry, I messed up. This question came from ETS’s OG.

Thank you. Yeah, I don’t know why the question posted twice. Didn’t mean to do that.

Sisi your answers are always detailed so thank you!

1 Like