i dont know how to do this

Question

Luis can drive 3times as fast as Carlos can ride his bicycle. If it takes Carlos 2 hours longer than Luis to travel 15miles, how fast can Carlos ride his bicycle? 



 

Answer 1

v = Carlos' speed = ?

3v = Luis' speed

travel distance = 15 miles

t = Luis' travel time 

t + 2 = Carlos' travel time

 

They both travel the same distance, which is the product of their speed and travel time.

 

(i)   v(t + 2) = 15

(ii)  (3v)t = 15

 

(ii) ⇒ t = 15/(3v) = 5/v

 

Plug into (i).

 

v(5/v + 2) = 15

5 + 2v = 15

 

v = (15 - 5)/2 = 5 miles/hour