A student studying for a vocabulary test knows the meanings

A student studying for a vocabulary test knows the meanings of 12 words from a list of 22 words. If the test contains 10 words from the study list, what is the probability that at least 8 of the words on the test are words that the student knows? (Round your answer to three decimal places.)

Solution

[8 known-2 unknown + 9 known-1 unknown + 10 known-0 unknown] / [any 10]

[12C8*10C2 + 12C9*10C1 + 12C10*10C0 ] / 22C10

=[ 495* 45 + 220*10 + 66*1] / 646646

= 0.03795