SSC CHSL 2024 PYQ — Question 68

The correct answer is option 4 i.e. 11.54 km/hr.

Average Speed = Total Distance / Total Time

Total Distance = 10  km + 15 km = 25  km

Time = Distance / Speed = 10 / 15 = 2 / 3  hours

Time = Distance / Speed = 15 / 10 = 1.5 hours

Total Time = 2 / 3 + 1.5

⇒ 1.5 = 3 / 2

⇒ $\frac{2}{3} = \frac{4}{6}, \quad \frac{3}{2} = \frac{9}{6}$

Total Time = 4 / 6 + 9 / 6 = 13 / 6  hours

Average Speed = $\frac{25}{\frac{13}{6}} = 25 \times \frac{6}{13} = \frac{150}{13} \approx 11.54$ km / hr