Question

A race car driver averages 159 miles per hour for 19 laps driven. How fast must he go in his 20th lap to attain an average of 160 miles per hour

Answer 1

179 mph

Explanation:

Given: Average speed to cover 19 lap is 159 mph

Now, finding the speed of driver in 20th lap to attain 160 mph as an average speed.

Average Speed =
`((average speed * lap covered) + speed in 20th lap)/(Total lap)`

Considering x as speed in 20th lap.

⇒ 160 =
`((159 * 19) + x)/(20)`

⇒ 160 =
`(3021 + x)/(20)`

Now, multiplying both side by 20.

⇒ 160
`* 20` =
`((3021 + x) * 20)/(20)`

⇒ 3200 =
`3021 + x`

∴ x = 179 mph

179 mph should be the speed of driver in his 20th lap to attain an average speed of 160 mph.