Question

A car travels for 10 minutes

at 30 km/h and then for
20 minutes at 45 km/h. What is the average speed for the whole journey

Answer 1

40 km/h

Explanation:

s = ut where s - Distance

u - Speed

t - Time

when t = 10 min

= 10/60 hours

S1 = 30 * 10/60

= 5km

when t= 20 min

= 20/60 hours

S2 = 45 *20/60

= 15 km

Then total distance = S1 + S2

= 5 + 15

= 20 km

Total time period = (10 + 20 ) / 60 hours

= 1/2 hours

Then average speed = U

S = UT

U = S/ T

= 20/ 0.5 km/ h

= 40 km/ h