Section A – Quantitative Ability

9. City Bus Corporation runs two buses from terminus A to terminus B, each bus making 5 round trips in a day. There are no stops in between. These buses ply back and forth on the same route at different but uniform speeds. Each morning the buses start at 7 AM from the respective terminuses. They meet for the first time at a distance of 7 km from terminus A. Their next meeting is at a distance of 4 km from terminus B, while travelling in opposite directions. Assuming that the time taken by the buses at the terminuses is negligibly small, and the cost of running a bus is ` 20 per km, find the daily cost of running the buses (in `).

A. 3200

B. 4000

C. 6400

D. 6800

E. None of the above.

Explanation:

Let the total distance be x. From 7:00 am to the first meeting, one bus covers 7 km, the other covers x – 7 km From the first meeting to the second the first bus covers x – 7 + 4 (or x – 3) and second covers 7 + (x – 4) or x + 3. The total is 2x.

\x – 3 = 2 (7) [or x + 3 = 2(x – 7)] Either equation gives x = 17. Five round trips represent a distance of

170 km or `3400 per bus.

\The total daily cost of running the two buses is `6800. Choice (D)