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CAT 1997 — QA Question 3

Basics of TSD/ProportinalityEasy
Passage / Data

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.

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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

Correct answer: 10 km/hr

  • A

    15 km/hr

  • B

    12 km/hr

  • 10 km/hr

  • D

    This is not possible

Solution

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 =(44x)+(2x)

His average speed over the race is 20 km/hr.

Hence, the time taken to complete the race = 620

Hence, we have the equation 44x+2x=620 Solving this equation, we get x = 10 km/hr.

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CAT 1997 QA Q3: Mr Tortoise completes the race at an average speed of 20 km/hr. His average speed for the first two stretches — Solution | TheCATExam