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( d) 32 m 75 cm and 14 m 25 cm (e) 109 g 379 mg and 55 g 312 mg
( f) 725 mL and 656 mL

3. The length of one piece of rope is 132 cm. Neha has another piece of ribbon measuring
188 cm. She places both the ribbons end-to-end. Find the length of the resultant
piece of ribbon.
4. Atul weighs 48 kg 250 g. Siya weighs 8 kg 125 g less than Atul. Find the weight of Siya.

5. There are two buckets full of water. The capacity of one bucket is 18 L 350 mL and
that of the other is 16 L 755 mL. How much water is there in both the buckets?

SPEED, DISTAnCE AnD TIME Enrichment

Speed tells us how fast an object or a person moves.
It is the rate of covering a distance in one unit of time. A speed of 50 km per hour means
that a distance of 50 km is covered in one hour.
Similarly, if a man walks 4 km in 1 hour, his walking speed is 4 km per hour.

Speed is calculated by dividing the distance travelled by the total time taken to travel that
distance. Thus, Speed = Distance ÷ Time.
We can get the following relationships from the above formula:

Distance = Speed × Time and Time = Distance
Speed
Units of Speed
The unit of speed will depend upon the unit of distance and the unit of time.

If the distance covered is in metres and time taken is in seconds, then the unit of speed
will be expressed in metres per second or m/s. It is the standard unit of speed.
If the distance covered is in kilometres and time taken is in hours, then the speed will be
expressed in kilometres per hour or simply km/h. Using the relationship between speed,
distance and time, we can calculate any one if the other two are given.

Example: Neha travelled a distance of 440 km by car in 10 hours. Find the speed of the car.
Solution: Distance travelled by car = 440 km
Time taken by car to travel 440 km = 10 hours
Speed = Distance ÷ Time = (440 ÷ 10) km/h = 44 km/h
Thus, the speed of the car is 44 km per hour or 44 km/h.

Think Tank Critical Thinking
1. A man travelled a distance of 260 km by car in 4 hours. What is the speed of the car?
2. A train runs at the speed of 85 km per hour. How much distance does it cover in 3
hours?

Knowledge Desk

Galileo was the first scientist to measure speed as a function of distance over time.

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