CAT 1997 — QA Question 3
Answer the next 3 questions based on the following information.
A certain race is made up of three stretches: A, B and C, each 2 km long, and to be covered by a certain mode of transport. The following table gives these modes of transport for the stretches, and the minimum and maximum possible speeds (in km/hr) over these stretches. The speed over a particular stretch is assumed to be constant. The previous record for the race is 10 min.
âââââââ
Mr Tortoise completes the race at an average speed of 20 km/hr. His average speed for the first two stretches is four times that for the last stretch. Find the speed over stretch C.
Answer & solution
- A
15 km/hr
- B
12 km/hr
10 km/hr
- D
This is not possible
Let his average speed over the last stretch be x.
Hence, his average speed for first two stretches = 4x. So the total time taken to cover the three stretches
His average speed over the race is 20 km/hr.
Hence, the time taken to complete the race =
Hence, we have the equation Solving this equation, we get x = 10 km/hr.