Question

A truck covers 10km with the speed of 50 km/h and further 10 km with the speed of 100 km/h then, what would be the average speed of the truck?
(1) 75 km/h
(2) 66.67 km/h
(3) 78 km/h
(4) 71.33 km/h​

Answer 1

speed =distance /time

time= distance /speed

t1=10/50=1/5 h

t2= 10/100=1/10 h

T =t1+t2=1/5+1/10=3/10h

S=s1+s2=150 km

average speed = S/T

=>20/3/10=200/3=66.67 km/h

Answer 2

time = distance/speed

T1=10÷50=1/5hrs

T2=10/100=1/10hrs

Tfinal=T1+T2

=3/10

S total=S1+S2

=150km

Vavg=200/3=66.67