Question

A bus covers $630$ km in $9$ h. If it completes the first two thirds of the journey at $60$ km/h, calculate its speed for the rest of the journey.

Answer 1

Total distance covered by the bus in $9$ h = $630$ km

Two third of the journey $=630\times \frac{2}{3}$ km

$=420$ km [Dividing the numerator by $3$]

Therefore, the distance for the rest of the journey $=630$ km $-420$ km

$=210$ km

Time taken by the bus to cover $420$ km at $60$ km/h is distance/speed $=\frac{420}{60}$ h

$=7$ h [Dividing the numerator and denominator by $60$]

Time left to cover the remaining $210$ km $=9$ h $-7$ h

$=2$ h

Therefore, the speed of the bus to cover $210$ km in $2$ h is distance/time $=\frac{210}{2}$ km/h

$=105$ km/h

Hence, the speed of the bus for the rest of the journey is $105$ km/h.