Question

Sujit covers a distance in 40 minutes if he drives at a speed of 60 kilometer per hour on an average. Find the speed at which he must drive at to reduce the time of the journey by 25%? *

Answer 1

Answer:  The required speed is 80 km per hour.

Step-by-step explanation:  Given that Sujit covers a distance in 40 minutes if he drives at a speed of 60 kilometer per hour on an average.

We are to find the speed at which Surjit must drive at to reduce the time of the journey by 25%.

Let x km be the distance covered by Surjit in 40 minutes at a speed of 60 kilometers per hour.

Then, we must have

$60=\dfrac{x}{\dfrac{40}{60}}\\\\\\\Rightarrow 60=\dfrac{3x}{2}\\\\\\\Rightarrow x=\dfrac{120}{3}\\\\\Rightarrow x=40.$

So, Surjit covers a distance of 40 km.

If we reduce the time by 25%, then the time taken by Surjit will be

$t=40-25\%\times40=40-\dfrac{25}{100}\times40=40-10=30~\textup{mins}=\dfrac{30}{60}=\dfrac{1}{2}~\textup{hour}.$

Therefore, the speed at which Surjit must travel to reduce the time by 25% is given by

$S=\dfrac{x}{t}=\dfrac{40}{\dfrac{1}{2}}=40\times2=80~\textup{km/hr}.$

Thus, the required speed is 80 km per hour.

Answer 2

Answer:

80 kmph

Step-by-step explanation:

so look at the pic ans is there