You guess on all of the answers on a 10 question quiz. If there are 4 possible answers for each question, what is the probability that you get 3 questions right?

Question

i've tried doing this problem multiple times and i'm just not understanding.. step by step would be very helpful.

Answer 1

prob of getting it right = 1/4
prob of getting it wrong = 3/4

prob of getting 3 of 10 right
= C(10,3) (1/4)^3 (3/4)^7
= 120(1/64)(2187/16384)
= appr .25