For how long (in seconds) must she walk? ?

Question

A golfer rides in a golf cart at an average speed of 3.06 m/s for 20.9 s. She then gets out of the cart and starts walking at an average speed of 1.21 m/s. For how long must she walk if her average speed for the entire trip, riding and walking, is 2.04 m/s

Answer 1

Let t sec. be the time spent walking.

Equating the sum of the times for the two parts of the journey to the total time multiplied by the average speed:

3.06 * 20.9 + 1.21t = 2.04(t + 20.9)

20.9(3.06 - 2.04) = (2.04 - 1.21)t

t = 25.7 sec.