How do you solve this word problem?

Question

Davie and Horatio are riding their motorbikes on a scenic tour that is 80 miles long. Davie rides at 20 miles per hour and leaves 90 minutes before Horatio. How fast must Horatio ride to finish at the same time as Davie?

Answer 1

20(t+1.5) = R t = 80

 

t + 1.5 = 4

 

t = 2.5

 

R = 80/2.5 = 32 <--- Horatio's speed

 

Horatio:

32 * 2.5 = 80

 

Davie

20 * (2.5 + 1.5) = 20 * 4 = 80