Question

A car travels 60 km in 1 hr 30 min.How long will it take to cover a distance of 100 km at the same speed.

Answer 1

Given: distance=60km , time=1hr,30min= 90mins Speed=d/t= 60/90=2/3 km per min To find time taken to cover a distance of 100km at speed 2/3kmpm, Time= distance÷speed =100÷2/3 =100×3/2 =150 mins

Answer 2

The time taken by the car to cover 100 km = 2 hr 30 mins.

The distance travelled by the car in 1hr 30 min is 60 km  

To find the time taken by the car to cover 100 km at the same speed  

Let $D_{1}$ be the distance travelled by the car =60 km

Let $T_{1}$ be the time taken by the car to cover 60km =1hr 30 min

Let $D_{2}$ be the distance travelled by the car =100 km

Let $T_{2}$ be the time taken by the car to cover 100 km=?

The well-known formula of speed is  

$Speed=\frac{\text {Distance}}{\text {Time}}$

Distance is directly proportional to time.

$\frac{D_{1}}{D_{2}}=\frac{T_{1}}{T_{2}}$

Converting 1hr 30 min in to hours $=1+\frac{1}{2}=\frac{3}{2}$ hours  

Substituting the value in the formula  

$\frac{D_{1}}{D_{2}}=\frac{T_{1}}{T_{2}}$

$\frac{60}{100}=\frac{\frac{3}{2}}{T_{2}}$

$\frac{60}{100}=\frac{3}{2 T_{3}}$

$\frac{1}{T_{2}}=\frac{2}{5}$

$T_{2}=\frac{5}{2}$

Convert $\frac{5}{2}$ into hr and minutes  

$\frac{5}{2}=2\ hours\ 30\ minutes$.