Subject: General Aptitude · Chapter: Time and Distance · Exam: 2008 · Marks: · Difficulty:
A boy rides his bicycle 10 km at an average speed of 12 km/hr and again travels 12 km at an average speed of 10 km/hr. His average speed for the entire trip is approximately
(a)10.4 km/hr
(b)10.8 km/hr
(c)11 km/hr
(d)12.2 km/hr
Answer
Answer (as printed): B
Explanation
Total distance travelled $=(10+12) \mathrm{km} / \mathrm{hr}=22 \mathrm{km} / \mathrm{hr}$. $$\begin{aligned} & \text { Total time taken }=\left(\frac{10}{12}+\frac{12}{10}\right) \mathrm{hrs}=\frac{61}{30} \mathrm{hrs} . \\ & \therefore \text { Average speed }=\left(22 \times \frac{30}{61}\right) \mathrm{km} / \mathrm{hr}=10.8 \mathrm{km} / \mathrm{hr} . \end{aligned}$$