Question

a boy runs for 20 minutes at a uniform speed of 18 km per hour at what speed should he Run for the next 40 minutes so that the average speed comes 24 km per hour

Answer 1

Answer:

The boy should run with a speed of 27 km/h for next 40 minutes.

Explanation:

Given that,

Time t₁ = 20 min =0.33 h

Speed = 18 km/h

Time t₂ = 40 min = 0.67 h

Average speed = 24 km/h

We need to calculate the distance

The distance  is the product of the speed and time.

$D = v\times t$

$D = 18\times0.33$

$D = 5.94\ km$

$D = 6\ km$

The distance will be after 40 min

$D' = 0.67\times v_{2}$

Now, The average speed is equal to the total distance divided by total time.

$v_{avg}=\dfrac{D+D'}{t_{1}+t_{2}}$

Put the value into the formula

$24=\dfrac{0.67\times v_{2}+6}{0.33+0.67}$

$v_{2}=\dfrac{24\times1.00-6}{0.67}$

$v_{2}= 26.86\ km/h$

$v_{2}=27\ km/h$

Hence, The boy should run with a speed of 27 km/h for next 40 minutes.

Answer 2

Answer:

Explanation:

It's a simple question but can be asked in ex . So here is the solution