Question : An athlete takes 1 minute 20 second to complete a race of 1000 meter. Find the speed of the athlete in kilometre per hour.
Correct Answer 45 km/h
Solution & Explanation
[Strategy to solve the Question: (1) Calculate the speed in m/s after changing the given time in second and then change this speed into kilometre per hour. (2) change the distance into km and time into minute and second, and then calculate the speed using these units. This speed will be in the required kilometer per hour]
Given,
Distance = 1000 meter
Time = 1 minute 20 second
= 1 × 60 second + 20 second
⇒ Time = 80 second
Now we know that,
Speed = Distance/Time
Thus, speed of the given athlete
= 1000 meter /80 second
= 12.5 meter per second
⇒ Speed = 12.5 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, 12.5 m/s
= 12.5 × 18 /5 km/h
= 45 km/h
Thus, speed of the given athlete = 45 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 = 1000 meter
= 1000 /1000 km = 1 km
[∵ 1000 meter = 1 km. Thus, 1 meter = 1 /1000 km]
Thus, distance = 1 km
And, given time = 1 minute 20 second
= 1 × 60 second + 20 second
⇒ Time = 80 second
= 80 /60 × 60 hour
= 8 2/360 90 hour
= 2/90 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
= 1 km /2/90 hour
= 1 km × 90/2 hour
= 45 km/h
Thus, speed of the given athlete = 45 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 using of type of method depends upon the situation. ]
Calculation of speed using Unitary Method when time and distance are given]
Given, Distance = 1000 meter
And, Time = 1 minute 20 second
= 1 × 60 second + 20 second
⇒ Time = 80 second
∵ In 80 second, the distance covered = 1 km
∴ In 1 second, the distance covered = 1 km /80 second
= 12.5 m/s or 12.5 meter per second
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, 12.5 m/s
= 12.5 m/1 s
= 12.5/1000 km /1/60 × 60 hour
= 12.5/1000 × 3600 km/h
= 12.5 × 3.6 km/h
= 45 km/h
Thus, speed of the given athlete = 45 km/h Answer
Similar Questions
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(2) By running at a speed of 17 km/h how much distance a motor bike will cover in 8 second?
(3) Find the distance covered by a bus in 24 hours if it covers a distance of 54 km in 14 hours.
(4) By running at a speed of 47 km/h how much distance a car will cover in 5 second?
(6) Find the distance covered by a motor bike in 23 hours if it covers a distance of 100 km in 13 hours.
(7) Find the distance covered by a cyclist in 21 hours if it covers a distance of 76 km in 11 hours.
(8) By running at a speed of 50 km/h how much distance a car will cover in 5 second?
(9) By running at a speed of 17 km/h how much distance a bus will cover in 9 second?