Ra'Ni-ya Reid-Cannon QI
A certain stylist charges $15 for a haircut and $30 for
hair coloring. A haircut takes on average 30 minutes,
while coloring takes 2 hours. The stylist works up to 8
hours in a day, and she needs to make a minimum
of $150 a day to pay for her expenses.

85.560%

step-by-step explanation:

conditional probability is defined as:

p(a|b) = p(a∩b) / p(b)

in other words, the probability that a occurs, given that b has occurred = the probability that both a and b occur / the probability that b occurs.

in this example:

p(turns 64 | turns 44) = p(turns 64 & turns 44) / p(turns 44).

if someone turns 64, they must have already turned 44, so:

p(turns 64 | turns 44) = p(turns 64) / p(turns 44)

on page 42, we see that of the original 100,000, 94944 turn 44, and 81234 turn 64.   therefore:

p(turns 64 | turns 44) = 81234 / 94944

p(turns 64 | turns 44) = 0.85560

the second option

step-by-step explanation: