Question

A car travel 10 km at a uniform speed of 20km/hr and next 20 km at a uniform speed of 10 km/hr. Find its average speed. *​

Answer 1

pls refer the attachment first for better understanding

$t1 = \frac{s1}{v1} = \frac{10}{20} = \frac{1}{2}$

$t2 = \frac{20}{10} = 2$

$avg \: speed = \frac{total \: distance}{total \: time}$

$avg \: speed = \frac{30}{ \frac{1}{2} + 2 } \\ avg \: speed = \frac{30}{ \frac{5}{2} } \\ avg \: speed = \frac{30 \times 2}{5} \\ avg \: speed = 12 \frac{m}{s}$

I hope this helps ( ╹▽╹ )

Answer 2

Answer:

A car travel 10 km at a uniform speed of 20km/h and next 20 km at a uniform speed of 10 km/h, its average speed is $12km/h$

Explanation:

• The average speed is defined as the total distance divided by the total time

        average speed=total distance /total time

From the question, it is given that

first traveled distance $d_{1} =10km$

uniform speed in this distance $V_{1} =20km/h$

time taken to cover the distance is given by the formula, $t=d/V$

⇒$t_{1} =10/20=0.5s$

during the second half, distance traveled $d_{2} =20km$

speed of the car over here $V_{2} =10km/h$

time taken is $t_{2} =20/10=2s$

so the average speed $V=\frac{d_{1} +d_{2} }{t_{1} +t_{2} }$

⇒$V=30/2.5=12km/h$