# Kangaroo question??

• February 19th 2011, 02:33 AM
hasanpak123
Kangaroo question??
26. A test is composed of ten questions each of which must be answered “a” or “b”. If you answer
any 5 questions „a” and any 5 questions „b”, the number of correct answers is guaranteed to be
at least 4. How many answer keys are there with this property?
A) 5^5 B) 252 C) 2 D) 10 E) 22
• February 19th 2011, 07:01 AM
TheEmptySet
Quote:

Originally Posted by hasanpak123
26. A test is composed of ten questions each of which must be answered “a” or “b”. If you answer
any 5 questions „a” and any 5 questions „b”, the number of correct answers is guaranteed to be
at least 4. How many answer keys are there with this property?
A) 5^5 B) 252 C) 2 D) 10 E) 22

$\underline{a},\underline{a},\underline{a},\underli ne{a},\underline{a},\underline{b},\underline{b},\u nderline{b},\underline{b},\underline{b}$