Question

A cyclist covers a distance of 750m in 2min 30sec. What is the speed of cyclist in \[km/hr\].

Answer 1

Hint::Distance- The length of line joining two given points is called the distance between them.
Unit of distance - meter (m), kilometer (km), centimeters (cm) etc.
Speed- Distance covered per unit time is called speed or we can say that ratio of distance and
time is known as speed.
Unit of speed - m/s (meter/second) , km/s(kilometer per second) , km/hr( kilometer per hour)
etc.
Formulae for speed, distance and time are –
Speed $ = \dfrac{{Dis\tan ce}}{{Time}}$
Distance $ = $ Speed $ \times $ Time
Time $ = \dfrac{{Dis\tan ce}}{{Speed}}$
We can easily learn the above formulas with the help of this triangle.

The positions of the words in the triangle will help us to learn these formulas.
To find the speed, distance is overtime in the triangle, so the speed is distance divided by time.
To find the distance, speed is beside time, so distance is speed multiplied by time.
Isn’t it an easy way of learning?

In above question we need to find out speed as units given in question and what they asked in answer is different units so first we need to convert the units
Like-
\[5km = \left( {5 \times 1000} \right)m = 5000m\]
\[5000m = \left( {5000 \times 100} \right)cm = 500,000cm\]
\[500,000cm = \left( {500,000 \times 10} \right)mm\]
\[ = 5000,000mm\]
\[5000,000mm = \left( {5000,000 \div 10} \right)cm\]
\[ = 5000,00cm\]
Complete step by step answer:
According to question -
Distance travelled by cyclist $ = $ 750m
Total Time taken by cyclist $ = $ 2min 30 sec
Speed in $km/hr = $ ?

By using the above chart first we will convert the units-
1. \[750m = 750 \div 1000 = 0.75km\]
2. \[2min\,30sec{\text{ }} = {\text{ }}2min + \left( {30 \div 60} \right)min\]
\[ = 2min + 0.5{\text{ }}min\]
\[ = 2.5{\text{ }}min\]
\[2.5{\text{ }}min = \left( {2.5 \div 60} \right){\text{ }}hrs\]
\[ = 0.0416{\text{ }}hrs\]
So now,
Distance \[ = 0.75{\text{ }}km\]
Time \[ = 0.0416{\text{ }}hrs\]
Now by using the formula for speed we will calculate the speed
Speed $ = \dfrac{{dis\tan ce}}{{time}} = \dfrac{{0.75}}{{0.0416}} = 18.02km/hr$
Therefore,
Speed of cyclist in km/hr is 18.02km/hr.
Note:
 For getting an answer in km/hr we can first solve the given question.
Then after getting speed in m/sec we can convert the answer in km/hr.
Like-
Distance $ = $ 750m
Time \[ = 2min{\text{ }}30{\text{ }}sec = \left( {2 \times 60} \right)sec + 30sec\]
\[ = 120 + 30 = 150sec\]
Speed $ = \dfrac{{dis\tan ce}}{{time}} = \dfrac{{750}}{{150}}m/\sec = 5m/hr$
$5m/\sec = 5 \div 1000km/\sec $
$ = \dfrac{5}{{1000}} \times 60 \times 60km/hr$
$ = 18km/hr$
So, speed $ = 18km/hr$
One more thing is to be noted is the difference between the answers obtained from both the methods.
From 1st method, we got 18.02 km/ hr and from 2nd we got 18km/hr.
So if it is a subjective question you can write any of the answers as magnitude as 18.02 is
approximately equals to 18.
And if it is a multiple-choice question you have to tick the answer according to the options available or if both are there then you should tick the perfect option which is 18.02 km/hr.