Suppose we flip four coins simultaneously: a penny, a nickel, a dime, and a quarter. What is the
probability that the penny and dime both come up the same?
[4! /2!*2!] / 2^4 =0.375 x 100 =37.5% - prob. of the penny and the dime coming up the same.
The nickel and quarter are irrelevant in this problem.
So the probability of both the penny and the dime landing on heads is 1/4, and the probability of them landing on tails is also 1/4. The probability of them coming up the same is thus 1/2.
We have 16 possible outcomes [2 for each coin = 2^4 = 16 ]
The penny and dime can both show tails...and there will be 2 * 2 = 4 outcomes for the other two coins
The penny and dme can both show heads...and there will be 2 * 2 = 4 outcomes for the other two coins
So....P ( penny and dime have the same results ) = is [ 4 + 4 ] / 16 = 8 / 16 = 1 / 2