Question

Find the distance covered by a car moving at 20 m/s for 3h.
A) 220 km
B) 218 km
C) 216 km
D) 230 km

Answer 1

Hint: Here first assume the distance covered by the car to be x
Then we will use the formula for speed and evaluate the value of distance x.
The speed is given by:-
\[{\text{speed}} = \dfrac{{{\text{distance}}}}{{{\text{time}}}}\]

Complete step-by-step answer:
Let the distance covered by the car be x
Now we are given that:-
Speed of the car is 20 m/s
The time taken by the car is 3 hours.
Since the time is given in hours and speed is given in m/s so we need to make the unit of time the same.
Hence in order to make the unit same, we will convert hours into seconds
Now since we know that:-
\[1hr = 60\min \] and \[1\min = 60\sec \]
Therefore,
\[1hr = 60 \times 60\sec \]
Hence 3hr will be equal to:-
\[3hr = 3 \times 60 \times 60\sec \]
Calculating the value we get:-
\[3hr = 10800\sec \]
Now we know that the speed is given by:-
\[{\text{speed}} = \dfrac{{{\text{distance}}}}{{{\text{time}}}}\]
Hence putting in the respective values we get:-
\[20 = \dfrac{x}{{10800}}\]
Now evaluating for the value of x we get:-
\[
  x = 20 \times 10800 \\
   \Rightarrow x = 216000m \\
 \]
Therefore, the distance covered is 216000 m
Now we will convert this distance into kilometers.
We know that:
\[
  1km = 1000m \\
   \Rightarrow 1 m = \dfrac{1}{{1000}}km \\
 \]
Hence 216000m will be equal to:-
\[216000m = \dfrac{{216000}}{{1000}}km\]
Calculating the value we get:-
\[216000m = 216km\]
Hence the distance covered by the car is 216 km

So, the correct answer is “Option C”.

Note: Students can also convert the speed from m/s to km/hour and then put the respective values in the formula for speed to get the value of distance covered.
\[1m/\sec = \dfrac{{18}}{5}km/hr\]