Question 952314
14/20=.7, 1-.7=.3
nCr=10C8=10!/((10-8)!*8!)=45
45*.7^8*.3^2
=.233
.
10C9=10
10*.7^9*.3
=.121
.
.7^10
=.028
.
.233+.121+.028
=.383 (rounding error)  the probability that at least 8 of the words on the test are words that the student knows.
.
Ed