In covering a distance of 144 km, Pranshu takes 3 hours more than Chandu. If Pranshu doubles his speed, then he would take 5 hour less than Chandu. Pranshu's speed is:

Correct option is D

Given:

Distance = 144 km

Pranshu’s time = Chandu’s time + 3 hours

If Pranshu doubles speed, his time = Chandu’s time − 5 hours

Formula Used:

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

Solution:

Let Pranshu’s speed = p km/h, Chandu’s speed = c km/h

From conditions:
$$​\frac{144}{p} = \frac{144}{c} + 3 .....(1) \\ \ \\​\frac{72}{p} = \frac{144}{c} - 5 .......(2)$$​​

​Subtract the second equation from the first:
​$$\frac{144}{p} - \frac{72}{p} = \left(\frac{144}{c} + 3\right) - \left(\frac{144}{c} - 5\right)$$​​

$$\frac{72}{p} = 8$$​​

p $$= \frac{72}{8} = 9$$​

Pranshu’s speed = 9 km/h.