Question

A rocket travels at a speed of 15000 m/s. Express this speed in km/hr.

Answer 1

Hint: In order to solve the above question, we will first convert meter into kilometer and second into hour, as we have been asked to get the speed in km/hr. unit. So we will convert m/s to km/hr. We will use the following conversions to solve this question,
\[\begin{align}
  & 1\text{ meter(m) = 1}{{\text{0}}^{\text{-3}}}\text{kilometer(km)} \\
 & \text{1 second(s) = }\dfrac{1}{3600}\text{hour(hr)} \\
\end{align}\]

Complete step-by-step answer:
We have been given the question that a rocket travels at a speed of 15000 m/s and we have been asked to express it in km/hr units.
So, we have, Speed = 15000 m/s
Now, we will have to convert meter into kilometer and second into hour by using the formula conversion,
\[\begin{align}
  & 1\text{ meter(m) = 1}{{\text{0}}^{\text{-3}}}\text{kilometer(km)} \\
 & \text{1 second(s) = }\dfrac{1}{3600}\text{hour(hr)} \\
\end{align}\]
So, the speed in (km/hr.)
\[\begin{align}
  & \Rightarrow \dfrac{15000\times {{10}^{-3}}}{\dfrac{1}{3600}} \\
 & \Rightarrow \dfrac{15}{\dfrac{1}{3600}} \\
 & \Rightarrow 15\times 3600 \\
 & \Rightarrow 54000km/hr \\
\end{align}\]
Therefore, the speed of the rocket in km/hr. is equal to 54000 km/hr.

Note: We can use the shortcut method to convert the speed in m/s to km/hr by simply multiplying the speed in m/s with 18 and then dividing the product of multiplication by 5, we can easily get the speed in km/hr.Also, you can remember that while converting the speed from km/hr. to m/s, we will just multiply the speed in km/hr. by $\dfrac{5}{18} $ and we will get the result in m/s.