Question

four coins are tossed what is the probability of two tails and two heads

Answer 1

This is a simple case of the Binomial Distribution, with n=4 and p=.5

The probability mass function of the Binomial Distribution is

nCx.(p^x)(1-p)^(n-x), C here is the combination function.

Using this function, the probability of getting x number of heads is:

(X)

4 heads 0 tails = 1/16

3 heads 1 tails = 4/16

2 heads 2 tails = 6/16

1 head 3 tails = 4/16

0 head 4 tails = 1/16

Cheers!