Question

To cover a certain distance, a man took 25 mins riding his bike at 80 km/h. He is found to be 5 mins late. What should be his speed if he has to reach on time?

• A. $90km/h$
• B. $100km/h$
• C. $110km/h$
• D. $95km/h$

Answer 1

The correct option is B $100km/h$

Given, a man covers a certain distance in 25 mins at 80 km/h.

The time that should be taken to reach on time = (25 - 5) = 20 mins (as he was late by 5 mins)

We know that to take less time to cover a certain distance, the speed should be more.

$\text{So, Time taken}\left(x\right)\propto \frac{1}{\text{Speed}\left(y\right)}$
$\therefore \frac{x_1}{x_2}=\frac{y_2}{y_1}$

Given,
$x_1=25mins$
$y_1=80km/h$
$x_2=20mins$
$\text{and}{y}_2=\text{the required speed}\text{to reach in 20 mins}$

$\Rightarrow y_2=\frac{x_1\times y_1}{x_2}$
$\Rightarrow y_2=\frac{25\times 80}{20}=100km/h$

Hence, the speed should have been 100 km/h.