Twenty identical coins each with probability $p$ of showing heads are tossed. If the probability of heads showing on $10$ coins is same as that of tails showing on $11$ coins, then $p$ is

A

$21 $

B

$2110 $

C

$2111 $

D

$2113 $

Medium

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Solution

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Correct option is C)

The probability of heads showing on $10$coins $=10p$ The probability of tails showing on $11$ coins $=11(1−p)$ according to question both are same => $10p=11(1−p)$ => $p=2111 $