Denise has 4 hours to spend training for an upcoming race. She completes her training by running full speed the distance of the race and walking back the same d

Question

Denise has 4 hours to spend training for an upcoming race. She completes her training by running full speed the distance of the race and walking back the same distance to cool down. If she runs at a speed of 7 mph and walks back at a speed of 3 mph, how long should she plan to spend walking back?

Answer 1

Hi Shatoria

 

To solve this problem, we need to recall the formula d = rd (distance = rates x time)

She runs at a speed of 7 _mph and walks at a speed of 3 mph.

 

Her distance running is 

d = 7t_r

where t_r is the time she spends running

 

Her distance walking is

d = 3t_w

where t_w is the time she spends walking

 

The distances are the same so

7t_r = 3t_w

 

We also know that the total time is 4 hours

t_r + t_w = 4

t_r = 4-t_w

 

Substitute this value of t_r in the first equation

7t_r = 3t_w

7(4-t_w) = 3t_w

28-7t_w = 3t_w

28 = 10t_w

2.8 = t_w

 

Denise will spend 2.8 hours (2 hours, 48 minutes) walking back and 1.2 hours (1 hour, 12 minutes running.