A coin is tossed 5 times. Find the probability that

a2linetagadaW

a2linetagadaW

Answered question

2021-09-19

A coin is tossed 5 times. Find the probability that all are tails. Find the probability that at most 2 are tails.

Answer & Explanation

Raheem Donnelly

Raheem Donnelly

Skilled2021-09-20Added 75 answers

Step 1
When a coin is tossed there are two possible outcomes {Head,Tail}.
Let x denote the number of tails which follows binomial with sample size 5 and probability of success 0.5(=12).
The Binomial probability distribution is:
P(X=x)=(beg{array}{c}nxend{array})(p)x(1p)nx
In the formula, n denotes the number of trails, p denotes probability of success, and x denotes the number of success.
The probability that all are tails is,
P(X=5)=(beg{array}{c}55end{array})(0.5)5(10.5)55
=1×0.03125×1
=0.03125
Thus, the probability that all are tails is 0.03125.
Step 2
The probability that at most 2 are tails is,
P(X2)=P(X=0)+P(X=1)+P(X=2)
=(beg{array}{c}50end{array})(0.5)0(10.5)50+(beg{array}{c}51end{array})(0.5)1(10.5)51+(beg{array}{c}52end{array})(0.5)2(10.5)52
=0.03125+0.15625+0.3125
=0.5
Thus, the probability that at most 2 are tails is 0.5.

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