A car travelling with $\dfrac{5}{7}$ of its actual speed covers 42 km in 1 hr 40 min 48 sec. Find the actual speed of the car.
17 $ \dfrac{6}{7}$ km/hr
25 km/hr
30 km/hr
35 km/hr
Explanation:
Time taken = 1 hr 40 min 48 sec = 1 hr 40$\dfrac{4}{5}$min=1$\dfrac{51}{75}$hrs=$\dfrac{126}{75}$hrs
Let the actual speed be x km/hr.
Then, $\dfrac{5}{7}x \times \dfrac{126}{75}$=42
$\Rightarrow \left( \dfrac{42\times7\times75}{5\times126}\right)$
=35km/hr.
Time taken = 1 hr 40 min 48 sec = 1 hr 40$\dfrac{4}{5}$min=1$\dfrac{51}{75}$hrs=$\dfrac{126}{75}$hrs
Let the actual speed be x km/hr.
Then, $\dfrac{5}{7}x \times \dfrac{126}{75}$=42
$\Rightarrow \left( \dfrac{42\times7\times75}{5\times126}\right)$
=35km/hr.