1 answer
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Which ways can two of the 15 coupons total $10?
2+8
5+5
8+2
P(2,8) = 5/15 * 2/14 = 1/21
P(5,5) = 2/15 * 1/14 = 1/105
P(8,2) = 2/15 * 5/14 = 1/21
Add up the ways and you get 11/105