Question

Sofia has a bag containing 8 blue beads and 7 red beads only.

She takes one bead out of the bag at random and replaces it.
She does this 90 times.
Find the number of times she expects to take a red bead.

Answer 1

The answer is 42 times.

Explanation:

The probability of taking out the red bead from the bag every time is

P = 7 ÷ (7 + 8) = 7/15

So, The number of times she expects to take a red bead is 'n'

Therefore,

n = 90 × 7/15

n = 6 × 7 = 42

Thus, The number of times she expects to take a red bead is 42.