Step-by-step explanation:
use the formula;
average speed = total distance/total time
if she walks at an average speed of 4 km/h for 90 minutes.
90 minutes = 1.5 hours
the distance she walked for 1.5hours;
4km/h x 1.5 hours = 6km
after reading for 15 mins she covers the same distance back to home. So total distance is 12 km.
she started walking at 6pm and arrived home at 8.3pm. so the total time spent walking and resting is 2.5 hours.
average speed= 12km/2.5h
= 4.8km/h
Therefore, Eileen's average speed as she runs back home is 4.8km/h
