Question

A scooter travels at 36 km/h for 5 hours and at 45 km/h for 4 hours. Find his average speed
for the whole journey

Answer 1

Distance travelled at 36 km/hr = 36*5 = 180 km

Distance travelled at 45 km/hr = 45*4 = 180 km

Distances are same:

Hence, Avg speed = 2*a*b/a+b, where a & b are speeds

Avg speed = 2*45*36/45+36 = 2*45*36/81 = 40 km/hr

Alternatively:

Avg speed= Tot Distance/Total Time = 180+180/5+4 = 360/9 = 40 km/hr

Answer 2

WE KNOW THAT SPEED =DISTANCE DIVIDED BY TIME

SO

36 DIVEDED  BY 5 IS 7.2

45 DIVEDED BY 4 IS 11.25

SO 7.2+11.25 DIVEDED BY 2 IS  14.85KM/HR