Question

Calculate the distance travelled by a man walking at a speed of $5km/h$in $36$minutes.
A. $3km$
B. $4km$
C. $5km$
D. $6km$

Answer 1

Hint: The speed of an object is defined as the distance travelled by the object in unit time.
The distance $d$ travelled by the object moving with speed $s$ in time $t$is given as,
$d = s \times t$.

Complete step by step answer:
You have given in the question speed of the man
$s = 5km/h$.
Time $t = 36$minute.
You have to find the distance $d$travelled by the man.

You first convert the units of time and speed to the same form either speed in $m/s$and time in $s$or speed $km/h$and time in $h$.
Here, speed in $km/h$ so you should convert time in $hour$.
You know, $1\min = \dfrac{1}{{60}}hour$so, $36\min $have,
$t = 36 \times \dfrac{1}{{60}}h$ .
When, speed $s$and time $t$ Then Distance $d$ is,
$d = s \times t$
Put values,
$d = 5km/h \times \dfrac{{36}}{{60}}h$
$d = 3km$.

So, the correct answer is “Option A”.

Additional Information:
1. To convert speed in $km/h$ to $m/s$you have to use below formula,
$1km/h = \dfrac{5}{{18}}m/s$.
You should also know how this formula come,
So, you know $1km$
$1h = 60\min $ and $1\min = 60\sec $,
So, $1h = 60 \times 60\sec $
Know,
$1km/h = \dfrac{{1000m}}{{60 \times 60s}}$
Simplify, $1km/h = \dfrac{5}{{18}}m/s$.
2. From the speed formula you can find any one unknown if you have given two known quantities.
i.e.
If speed $s$and time $t$is given then, you can find third unknown distance $d$ by making use of below formula,
$d = s \times t$
If speed $s$ and distance $d$ is given then, you can find time $t$ required use below formula,
$t = \dfrac{d}{s}$
If distance $d$ and time $t$is given the speed $s$ of the object is given as,
 $s = \dfrac{d}{t}$.

Note:
You should always check the units of speed, distance and time. If speed in $km/h$then, time should be in $h$ and distance in $km$. Same for other units.