You are given an unfair coin (i. e. a coin where the probability of it landing on either side is NOT 1/21/2) and told that the probability of getting at least one tails in three tosses of said coin is 26/2726/27. The probability of getting heads in one toss of the unfair coin can be expressed in the form M/NM/N, where MM and NN are relatively prime positive integers (i. e. their greatest common divisor is 1). Compute M + NM+N

Here we have a problem of probability, we will find that the probability of landing in heads is M/N = 1/3, then we have:

M + N = 1 + 3 = 4.

Let's see how we got that:

Let's define:

p = probability of landing on tails

q = probability of landing on heads.

The probability of getting at least one tails in 3 tosses is 26/27

This means that the probability of not getting tails in the 3 tosses is:

P = 1 - 26/27 = 1/27

And the case where you do not get any tails in the 3 tosses, means that in all the 3 tosses you got heads.

The probability of getting 3 heads in a row is:

P = q^3 = 1/27

Solving for q, we get:

q = ∛(1/27) = 1/3

Now we want to express q = M/N = 1/3

then we have:

M = 1

N = 3

Now we want to compute M + N = 1 + 3 = 4

If you want to learn more about probability, you can read: