A car travelling with $\frac{5}{7}$th of its actual speed covers 42 km in 1 hr 40 min 48 sec. Find the actual speed of the car.

Question and options

A car travelling with

\frac{5}{7}

th of its actual speed covers 42 km in 1 hr 40 min 48 sec. Find the actual speed of the car.

Correct answer: B - 35 km/hr

1 hr 40 min 48 s =

1 + \frac{40}{60} + \frac{48}{3600} = 1.68

h. Speed at

\frac{5}{7}

of actual =

\frac{42}{1.68} = 25

km/h, so actual speed =

25 \times \frac{7}{5} = 35

km/h.