Gavin has a collection of 50 songs that are each 3 minutes in length and 50 songs that are each 5 minutes in length. What is the maximum number of songs from his collection that he can play in 3 hours?
(A) 100
(B) 36
(C) 56
(D) 60
(E) 45
To maximize the number of songs used, Gavin should use as many of the shortest length songs as possible. (This is because he can always trade a longer song for a shorter song and shorten the total length used.)

If Gavin uses all 50 songs of 3 minutes in length, this takes 150 minutes.

There are $180-150=30$ minutes left, so he can play an additional $30 \div 5=6$ songs that are 5 minutes in length.

In total, he plays $50+6=56$ songs.

ANSWER: (C)