Answer:
10 times.
Step-by-step explanation:
He rolls all the dice independently, so The expected number of 3's is 60 * (expected number of 3's in one throw).
The expected number of 3's in one throw is:
5/6 * 0 + 1/6 * 1 = 1/6
because 5/6 of the time we roll zero 3's and 1/6 of the time we roll one 3 :D
So he should expect (60 * 1/6 = 10) 3's in 60 throws.
