A coin is tossed 7 times and the sequence of

Ahmed Stewart

Ahmed Stewart

Answered question

2022-01-23

A coin is tossed 7 times and the sequence of heads and tails are observed. So, how many different sequences have at least 3 heads?

Answer & Explanation

lirwerwammete9t

lirwerwammete9t

Beginner2022-01-24Added 9 answers

In order to obtain the number of sequences of at least 3 heads, you should subtract the number of sequences for 0 head, 1 head and 2 heads from total number of sequence.
Total number of sequences is 2×2×2×2×2×2×2=27=128
The number of sequences for 0 heads: 1
The number of sequences for 1 head:7
The number of sequences for 2 head: 6+5+4+3+2+1=21
Total number of sequences for 0 head, 1 head and 2 heads is 1+7+21=29.
Therefore, the number of sequences of at least 3 heads is 12829=99

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