Question

A car moves through $20\text{km}$ with a speed of $40\text{km/hr}$ and the next $20\text{km}$ with a speed of $60\text{km/hr}$. Calculate its average speed.

• A. $45\text{km/hr}$
• B. $48\text{km/hr}$
• C. $52\text{km/hr}$
• D. $58\text{km/hr}$

Answer 1

The correct option is B $48\text{km/hr}$

We know that, average speed,

$v_{\text{av}}=\frac{\text{Total Distance}}{\text{Total Time}}$

$\Rightarrow v_{\text{av}}=\frac{20+20}{\frac{20}{40}+\frac{20}{60}}[\because v=\frac{d}{t}]$

$\Rightarrow v_{\text{av}}=48\text{km/hr}$