Page 134 - ICSE Math 7

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6. A train travelling with a speed of 70 km h leaves Patna at 8 a.m. and another train travelling at
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90 km h leaves Patna at 10 a.m. Both the trains are travelling in the same direction. How many
kilometres from Patna will they meet?

AT A GLANCE

¾ The distance covered by a body in unit time is called its speed.
¾ If a body covers equal distances in equal intervals of time, then its speed is said to be uniform,
otherwise its speed is non uniform.
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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 m s into km h , multiply by 18 .
5
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¾ To convert speed in km h into cm s , multiply by 250 .
9
9
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¾ To convert speed in cm s into km h , multiply by 250 .
Total distance covered
¾ Average speed =
Total time taken
¾ Relative speed is the speed of one object with respect to other object.

MENTAL MATHS

1. Write True or False.
(a) If an object covers equal distances in equal intervals of time, its speed is said to be uniform.
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(b) If time is in minutes and speed is in km min , then distance covered is in kilometres.
(c) When two bodies are moving in the same direction, their relative speed is equal to the sum
of their speeds.
(d) Average speed of a body is the product of total distance covered and the total time taken by
the body.

2. Fill in the blanks.
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(a) An aeroplane travels 700 km in 50 minutes. Its speed in km h is _________.
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(b) A train 220 m long, travels at a uniform speed of 36 km h . It will take _________ s to pass
an electric pole.
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(c) A boat can travel with a speed of 13 km h in still water. If the speed of the stream is 7 km h ,
then the speed of the boat upstream is _________.
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(d) Rohan crosses a platform in 5 minutes with a speed of 1.5 m s . The length of the platform
is _________.

PRACTICE TIME

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1. Two cars start from the same point at 64 km h and 47 km h . Find the distance between them
after 12 minutes, if they travel:
(a) in the same direction.
(b) in opposite directions.

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