Page 128 - ICSE Math 6

AT A GLANCE

¾ The speed of a body is the distance covered by the body in unit time.
Distance Distance
¾ Speed = ; Distance = Speed × Time; Time =
Time Speed
Total distance covered
¾ Average speed =
Total time taken
¾ If a body covers equal distances in equal intervals of time, then its speed is uniform, otherwise
its speed is variable.
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¾ To convert speed in km h into m s , multiply by 5 .
18
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¾ To convert speed in km h into cm s , multiply by 250 .
9
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¾ To convert speed in m s into km h , multiply by 18 .
5
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¾ To convert speed in cm s into km h , multiply by 9 .
250
MENTAL MATHS

1. Write True or False.

(a) The average speed of a body is calculated by dividing the total distance travelled by total
time taken.
(b) The distance travelled by a body is the speed of the body divided by unit time.
(c) If a car travels equal distances in equal intervals of time, then its speed is uniform.
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(d) If distance is in metres (m) and time is in minutes (min), then speed is in m min .
2. Fill in the blanks.
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(a) Amit covers the first 10 km at a speed of 30 km h , the next 10 km at a speed of 35 km h
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and the remaining distance at a speed of 30 km h . So, Amit has a ____________ speed.
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(b) A distance of 60 metres is covered in 6 seconds. So, the speed is ____________ m s .
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(c) If speed = 8 km min and time = 30 min, then distance covered = ____________ km.
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(d) If speed = 16 m s and distance covered = 1.92 km, then time taken = _______ s = _______min.
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(e) If distance = 25 km and time taken = 50 min, then speed = ____________ km h .

PRACTICE TIME

1. Convert the following speeds.
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(a) 81 km h into cm s (b) 275 m s into km h –1
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2. How much distance does an athlete cover in 1 hour if he runs at a speed of 550 m min ?
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3. A 115 m long train is running at a speed of 140 m min . How much time will it take to cross a
305 m long platform?
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4. A car going at a speed of 70 km h takes 4 hours to reach its destination. How much time will
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another car take to cover the same distance at a speed of 40 km h ?

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