Question

David and Josh are both practicing for an upcoming swim tournament. Every week, David swims for 3x hours at an average speed of x laps per hour. Josh swims 5 more hours per week than David, but at an average speed that is 4 laps per hour less than David's average speed.
Which of the following functions will give the total distance, in laps, that Josh swims each week?

A) f(x)=3x^2-17x+20

B) f(x)=3x^2+7x-20

C) f(x)=3x^2-7x-20

D) f(x)=3x^2+17x+20

Answer 1

Josh swims 5 more hours per week than David so his hours = 3x + 5

His average speed is 4 laps per hour less than David's so it is = x - 4

Total distance = hours * speed
= (3x + 5)*(x - 4)
= 3x^2 - 7x - 20

Ans is C