Find the rate of each jogger

Question

Two joggers start at the same time from opposite ends of a boardwalk that is 12kilometers long. One jogs twice as fast as the other. Find the rate of each jogger of they meet at 15 minutes. 

 

 

 

Answer 1

If the first jogger jogs at rate r then the 2nd jogger jogs at rate 2r. The time they both travel is 15 min or .25 hr. 

Since distance = rate*time and the sum of the distances must equal 12 km. 

 

r(.25)+2r(.25)=12km

.75r=12

r=16 km/hr and the faster jogger is 

twice that so 32km/hr

Answer 2

Suppose the slower runs at x km/hr; then the other guy's rate must be 2x.

 

Slow guy covers distance D = RT =(x)(¼) because 15 min is a quarter of an hour.

Fast guy covers the rest of the distance, 12-D (so that the two distances add up to 12); his distance 12-D = (2x)(¼).

 

If we add these two, we get 12 km = (3x)(¼).  I wil llet you solve for x, the slow guy's speed, in km/hr.

Answer 3

Duplicate submission. I'll answer the first one.