Question

A girl leaves her home A at 9am, and after cycling for 25km at 5km/h she reaches her destination B at 2pm. After having lunch at B for 90 minutes, she sets off for home. On the way home she stops for half an hour to see a friend who lives at C, which is 10km from A. At 5:30pm, she leaves C and cycles until she reaches home at 7pm.

a) What was the girls speed from B to C?
b) What was her speed from C to home?

Answer 1

what's the problem? Just calculate the distance and time as needed, and the average speed is distance/time.

For (a),
A-B is 25km
A-C is 10km
So, B-C is 15km

C-A takes 1.5 hr
B-A takes 3.5 hr
stop at C takes 0.5 hr
So, the B-C leg takes 1.5 hr

15km/1.5hr = 10km/hr

The rest is now easy, given the above data.