Question:
An athlete takes 45 second to complete a race of 600 meter. Find the speed of the athlete in kilometre per hour.
Correct Answer
45 km/h
Solution And Explanation
[Strategy to solve the Question: (1) Calculate the speed in m/s and then change this speed into kilometre per hour. (2) change the distance into km and time into hours and then calculate the speed using these units. This speed will be in the required kilometer per hour]
Given,
Distance = 600 meter
Time = 45 second
Now we know that,
Speed = Distance/Time
Thus, speed of the given athlete
= 600 40 meter /45 3 second
= 40/3 m/s
⇒ Speed = 40/3 m/s
Conversion of speed from m/s to km/h
To convert meter per second (m/s) to kilometre per hour (km/h) we need to multiply m/s by 18 /5 .
Thus, 15 m/s
= 40 8/3 × 18 6 /5 km/h
= 8 × 6 km/h = 48 km/h
Thus, speed of the given athlete = 48 km/h Answer
Second method to calculate the speed in km/h using distance given in meter and time given in second.
Here, given distance = 600 meter
= 600 /1000 km
[∵ 1000 meter = 1 km. Thus, 1 meter = 1 /1000 km]
= 6 /10 km
Thus, distance = 0.6 km
And, given time = 45 second
= 45 /60 × 60 hour
= 45/3600 hour
= 0.0125 hour
Thus, time = 0.0125 hour
Calculation of speed in km/h using formula
Now we know that,
Speed = Distance/Time
Thus, the speed of the given athlete in km/h
= 0.6 km /0.0125 hour km
= 48 km/h
= 48 kilometer per hour
Thus, speed of the given athlete is 48 km/h Answer
[After observing the result obtained here, it is better to calculate the speed in m/s using the given units and after that change the speed from m/s to the required km/h. The use of the type of method depends upon the situation. ]
Calculation of speed using Unitary Method when time and distance are given
Given, Distance = 600 meter
= 600/1000 km
⇒ Distance = 0.6 km
And, Time = 45 second
= 45/60 × 60 hour
= 0.0125 hour
∵ In 0.0125 hour, the distance covered = 0.6 km
∴ In 1 hour, the distance covered = 0.6 km /0.0125 hour
= 45 km/h
Thus, speed of the given athlete = 45 km/h Answer
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(3) By running at a speed of 38 km/h how much distance a scooty will cover in 7 second?
(4) By running at a speed of 34 km/h how much distance a motor bike will cover in 8 second?
(5) Find the distance covered by a cyclist in 21 hours if it covers a distance of 78 km in 11 hours.
(6) By running at a speed of 43 km/h how much distance a scooty will cover in 7 second?
(7) Find the distance covered by an athlete in 25 hours if it covers a distance of 66 km in 15 hours.
(8) Find the distance covered by a scooty in 22 hours if it covers a distance of 70 km in 12 hours.
(9) At a certain speed a cyclist covers a distance of 80 km in 3 hours. How much distance will it cover in 4 hour?
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