Question

Amit’s school bus travels at 36 km/h and Sushma’s school bus travels at 11 km/s, whose school bus travels faster?

Answer 1

Hint: As we can see both the speeds are given in different units here, so to find the answer, we need to change any one of the units into the other unit. So, we will change km/h into m/s. We know that $1km=1000m$ and $1h=60\times 60s$, so we will get, $\dfrac{1km}{h}=\dfrac{1000m}{3600s}=\dfrac{5m}{18s}$. Then we will find the difference between both the speeds.

Complete step by step solution:
We have been given that Amit’s school bus travels at a speed of 36 km/h and that Sushma’s school bus travels at a speed of 11 m/s. And we have been asked which school bus travels faster. So, since both the speeds are given to us in different units, we need to convert them into the same units before comparing. So, we will first convert the speed of Amit’s school bus from km/h to m/s. Now, we know that $1km=1000m$ and $1h=60\times 60s$. So, we get 1 km/h in m/s as,
 $\dfrac{1km}{h}=\dfrac{1000m}{3600s}=\dfrac{5m}{18s}$
So, we can convert 36 km/h into m/s as follows,
$\begin{align}
  & 36\dfrac{km}{h}=36\times \dfrac{5m}{18s} \\
 & \Rightarrow 36\dfrac{km}{h}=2\times \dfrac{5m}{s} \\
 & \Rightarrow 36\dfrac{km}{h}=10\dfrac{m}{s} \\
\end{align}$
So, we get the speed of Amit’s school bus as 10 m/s. And we know that the speed of Sushma’s school bus has been given as 11 m/s. So, we can clearly see that Sushma’s school bus has a greater speed and so it will travel faster than Amit’s school bus. The difference in their speed is, $11\dfrac{m}{s}-10\dfrac{m}{s}=1\dfrac{m}{s}$ or 1 m/s.
Therefore, Sushma’s school bus travels faster than Amit’s school bus by 1 m/s.

Note: The possible mistakes that students can make is that they do not notice the units of the given speed and directly say that Amit’s school bus travels faster than Sushma’s school bus, just by looking at the numbers, that is 36 and 11, ignoring the units. This will lead to an incorrect answer as they will find the difference also as 36 - 11 = 25.