## Topic outline

• ### Time

• Time (Speed, Distance and Time)

Ria reaches her school in 10 minutes whereas her friend Dia takes 15 minutes to reach. This mean Ria takes lesser time than her friend Dia to reach school.

In the above, the word ‘time’ has been used. Time is measured in seconds, minutes and hours.

When distance and speed are given in the question we measure time in the following way.

Illustration 1: How much time will be taken to cover a distance of 100 km at a speed of 10 km per hour?

Solution:

Time taken to cover 10 km = 1hr.

Time taken to cover 1 km = 1/10 hrs.

Time taken to cover 100km

= 1/10 x 100

= 10 hrs.

Illustration 2: A car covers a distance of 150 km at a speed of 50 km/hour. Find the time taken to cover this distance.

Solution:

Time = distance/speed

Time = 150 km/(50 km/hour)

= 3 hours.

Illustration 3: A motor cyclist covers a distance of 20 km at a speed of 10km per hour. Calculate the time taken to cover this distance.

Solution:

Speed = 10 km/hour

Distance covered = 20 km

Time = distance/speed

= 20/10 hour

= 2 hours

Illustration 4: A boy runs at a speed of 20 m per minute. How much time will be taken to cover a distance of 1km?

Solution:

20 m is covered in 1 min

1 m is covered in 1/20 min

1000 m (i.e. 1km) is covered in 1/20 x 1000 = 50 min