Question

It is estimated that 78% of drivers use their turn signal. How many people should a police officer expect to pull over until she finds a driver not using the turn signal?

A) 5
B) 3
C) 4
D) 2
E) 6

Answer 1

They should expect to pull over 5 people.

Answer 2

Given

Let P = Percentage of people using signal

`\text{P} = 78\%`

Let Q = Percentage of people not using signal

`\text{P + Q} = 1` ---- Make Q the subject of formula

`\text{Q} = 1 - 78\%`

`\text{Q} = 1 - 0.78`

`\text{Q} = 0.22`

The expected number of people is calculated as 1/Q

`= (1)/(0.22)`

`= 4.54`

`= 5` ---- Approximated

Hence, the expected number of people a police officer expects to pull over until she finds a driver not using the turn signal is 5