Combination Question I don’t understand

pka

Elite Member
Joined
Jan 29, 2005
Messages
8,319
The answer for Q 15, C is 42. But I don’t know how to get it. Plz help
There are four classical CDs. So at least three means three or four.
He selects five. So include three or four classical and two or one other.
Look at this It seems 42 is incorrect.
 

Romsek

Full Member
Joined
Nov 16, 2013
Messages
336
I'm seeing the answer as 66 ways.

\(\displaystyle \dbinom{4}{3}\dbinom{6}{2}+\dbinom{4}{4}\dbinom{6}{1} = 66\)
 

Harry_the_cat

Senior Member
Joined
Mar 16, 2016
Messages
1,385
I'm with Romsek.
 

Jomo

Elite Member
Joined
Dec 30, 2014
Messages
3,652
Yeah, pka and Romsek are correct.
 

Snickey

New member
Joined
Apr 10, 2019
Messages
3
Oh alright, I got the same answer too. Guess Cambridge got it wrong. Thanks everyone!
 
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