We will discuss how to express speed in different units. Speed in km/hour can also be expressed in meter per minute or metre per second.
Now we will learn to express given speed in km per hour into speed in metre per minutes or metre per second.
For this, we should remember the following conversion:
1 km = 1000 m
1 m = \(\frac{1}{1000}\) km
1 minute = \(\frac{1}{60}\) hour
1 minute = 60 seconds
1 second = \(\frac{1}{60}\) minute
Solved examples to express speed in different units:
1. The speed of a train is 45 km per hour. Calculate its speed in metres per second.
1 km = 1000 m
1 hour = 60 minutes; 1 minute = 60 seconds
1 hour = 60 × 60 seconds
Speed of the train = \(\frac{45 km}{1 hour}\)
= \(\frac{45 × 1000 m}{60 × 60 sec }\)
= \(\frac{25}{2}\) m/sec
= 12\(\frac{1}{2}\) m/sec.
2. Convert the following speed as desired.
(i) 80 meter per minute into km per hour
Speed = distance/time
= \(\frac{80 meters}{1 minute}\)
= \(\frac{\frac{80}{1000 km}}{\frac{1}{60 hour}}\)
= \(\frac{80}{1000}\) × \(\frac{60}{1}\) km per hour
= \(\frac{24}{5}\) km per hour
= 4\(\frac{4}{5}\) km/hr
(ii) 20 m/second into km/hour
1 km = 1000 m
or, 1 m = \(\frac{1}{1000}\) km
20 m = \(\frac{20}{1000}\) km
1 hour = 60 × 60 = 3600 seconds
1 second = \(\frac{1}{3600}\) hour
But speed = distance ÷ time
= \(\frac{20}{1000}\) ÷ \(\frac{1}{3600}\)
= \(\frac{20}{1000}\) × 3600 km/hour
= 72 km/hour
To find Speed when Distance and Time are given.
To find the Distance when Speed and Time are given.
To find Time when Distance and Speed are given.
Worksheet on Speed, Distance and Time.
5th Grade Numbers
5th Grade Math Problems
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