Question

River boat ( ) a river boat leaves silver town and travels upstream to gold town at an average speed of 6 kilometers per hour. it returns by the same route at an average speed of 9 kilometers per hour. what is the average speed for the round-trip in kilometers per hour?

a.7.0

b.7.1

c.7.2

d.7.5

e.8.0

Answer 1

Let's suppose the distance between gold town and silver town is 9 kilometers.

The first trip takes 9 km / 6 km / hour = 1.5 hours

The return trip takes 9 / 9 km / hour = 1 hour

TOTAL TRIP = 18 kilometers in 2.5 hours

= 18 / 2.5 = 7.2 hours

Answer is c

Explanation: