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Question
A coin is tossed 8 times. In how many ways can we obtain at least 6 heads?
Solution
A coin is tossed 8 times. All heads are identical and all tails are identical.
When at least 6 heads are to be obtained
∴ Outcome can be (6 heads and 2 tails) or (7 heads and 1 tail) or (8 heads)
∴ Number of ways in which it can be obtained
= `(8!)/(6!2!)+(8!)/(7!1!)+(8!)/(8!)`
= `(8 xx 7)/2+8+1`
= 28 + 8 + 1
= 37
∴ In 37 different ways we can obtain at least 6 heads.
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