試題詳解

156. On a block of ten houses, k are not insured. A tornado randomly damages three houses on the block.

The probability that none of the damaged houses are insured is 1/120.

Calculate the probability that at most one of the damaged houses is insured.
(A) 1/5
(B) 7/40
(C) 11/60
(D) 49/60
(E) 119/120