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 x $ =$ \left(\dfrac{42 \times 7 \times 75}{5 x 126} \right) $= 35 km/hr. |