Common Core: S-CP.2
Problem 12 of 25sta-012
A drawer holds 4 blue socks and 6 green socks. Two socks are drawn at random, one at a time, without replacement. What is the probability that both are the same color?
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Solution walkthrough1:54
- Same color can happen two ways: blue then blue, or green then green. Find each chance, then add.
- First sock: of the socks are blue and of the are green.
- The first sock stays out, so are left. After a blue, of are blue. After a green, of are green.
- Multiply along each path: and .
- Either path gives a match, so add: .
- Traps: and each count one color only. puts the first sock back.