Question

A car covers a certain distance in 35 min, if it runs at 60 km/hr. How much time will it take to cover the same distance at a speed of 45km/hr?

Answer 1

Hint: We start solving the problem by assigning the variable for the total distance travelled by the car. We then recall the relation between speed, distance and time as distance = speed $\times $ time. We find the given time in minutes and substitute the values in the formula to find the distance travelled. We then find the time required to travel this distance if the car travelled at a speed of 45km/hr using $time=\dfrac{\text{distance}}{speed}$.

Complete step by step answer:
According to the problem, we are given that a car covers certain distance in 35 min, if it runs at 60 km/hr. We need to find the time required to cover the same distance if the car travels at a speed of 45 km/hr.
Let us assume the distance travelled be ‘x’ km. We know that distance = speed $\times $ time.
Let us convert the given time 35 min into hours. We know that $1hour=60\min \Leftrightarrow 1\min =\dfrac{1}{60}hour$.
So, we get $35\min =\dfrac{35}{60}hours$.
Now, we have $x=60\times \dfrac{35}{60}=35km$.
We have found that the car travelled a distance of 35 km.
Now, we need to find the time required by the car to travel this distance if it travels at a speed of 45 km/hr. Let us assume the time required be ‘t’ hours.
We know that $time=\dfrac{\text{distance}}{speed}$.
$\Rightarrow t=\dfrac{35}{45}hours$.
We know that 1 hour = 60 mins.
$\Rightarrow t=\dfrac{35}{45}\times 60=\dfrac{140}{3}\min $.

∴ The time required by the car for travelling a distance of 35 km at 45 km/hr is $\dfrac{140}{3}\min $.

Note: We need to make sure that the units are similar for time, speed and distance before solving the problem. We cannot use time in mins if the speed is given as km/hr as this will lead us to the wrong answers. We should perform every step carefully in order to avoid calculation mistakes. Similarly, we can expect problems to find the percentage difference in the time taken to travel.