Question

a bus travels, first half of its distance with a speed of 40km per hour.and next half with a speed of 60km per hour.find average speed of the bus​

Answer 1

Explanation:

let the total distance be s

let the time be T and t

so,

speed=distance/time

40=s/2T

T=s/80-------(1)

60=s/2t

t=s/120------(2)

as we know

average speed=total distance/total time----(3)

total time=T+t

from equ. 1 and 2

total time=(s/80)+(s/120)

total time=s/48

from eq 3

average speed=(s*48)/s

average speed=48km/hr

shortcut formula:-

let the speed be v1 and v2

so,

average speed=(2*v1*v2)/(v1+v2)

average speed=(2*40*60)/(40+60)

average speed=4800/100

average speed=48km/hr