A car moves with a speed of $40\ km/h$ for 15 minutes and then with a speed of $60\ km/h$ for the next 15 minutes. The total distance covered by the car is:
$(i).\ 100\ km$
$(ii).\ 25\ km$
$(iii).\ 15\ km$
$(iv).\ 10\ km$

The correct answer is $(ii).\ 25\ km$

Explanation:

Given:

A car moves with a speed of $40\ km/h$ for 15 minutes and then with a speed of $60\ km/h$ for the next 15 minutes. 

To do:

To find the total distance covered by the car.

Formula to be used:

$ Distance = Time\times Speed$

When the car moves with a speed of $40\ km/h$ for 15 minutes:

Distance$_{1}=15 min \times 40 km/h$

$=\frac{15}{60}\ h\times 40\ km/h$

$=10\ km$

When the car moves with a speed of $60\ km/h$ for the next 15 minutes:

Distance$_{2}=15\ min\times 60\ km/h$

$=\frac{15}{60}\ h\times 60\ km/h$

$=15\ km$

Total distance $=Distance_1+Distance_2$

$=10\ km + 15\ km$

$=25\ km$

Therefore, the total distance covered by the car is $25\ km$.