Question

Express the following speed in $km/hr$:

$270min12sec$

Answer 1

STEP 1 : Finding the speed in $\mathit{m}\mathbf{/}\mathit{s}$

We know that, $Speed=\frac{dis\tan cetravelled}{timetaken}$

Speed $=\frac{270}{12}=22\frac{1}{2}m/s$

Speed $=22\frac{1}{2}=\frac{22\times 2+1}{2}=\frac{45}{2}m/s$

STEP 2 : Converting the speed from $\mathit{m}\mathbf{/}\mathit{s}$ to $\mathit{k}\mathit{m}\mathbf{/}\mathit{h}\mathit{r}$.

We know that, $1m/s=\frac{18}{5}km/hr$

$\Rightarrow \frac{45}{2}m/s=\frac{45}{2}\times \frac{18}{5}km/hr$

$\Rightarrow \frac{45}{2}\times \frac{18}{5}=9\times 9=81km/hr$

Hence, $270min12sec$ can be expressed as $81km/hr$.