Question

a bus travelling the first one third distance at the speed of 10 km per hour then its one fourth at 20 km per hour and the remaining at 40 km per hour what is the average speed of the bus​

Answer 1

Average speed = Total distance / Time

= S / (t1 + t2)

= S / [(S/(3 * 10)) + (S/(4 * 20)) + (5S/(12 * 40))]  

...….....[∵ Time = Distance / Speed]

= 1 / (1/30 + 1/80 + 5/480)

= 17.7 kmph

Answer 2

average speed=total distance/total time

let the distance be x,

remaining distance=x-1/3x-1/4x

=12x-4x -3x /12x

=5x/12x=5/12

average speed=10+20+40/1/3*10+1/4*20+5/12*40

=70/40+60+200/12

=12*70/300

=2.8kmph