Meeting cars speed ratio

CAT 2020 Slot 1 · QA · Easy · Speed, Time & Distance

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A straight road connects points A and B. Car 1 travels from A to B and Car 2 travels from B to A, both leaving at the same time. After meeting each other, they take 45 minutes and 20 minutes, respectively, to complete their journeys. If Car 1 travels at the speed of 60 km/hr, then the speed of Car 2, in km/hr, is

  1. A.

    90

  2. B.

    80

  3. C.

    70

  4. D.

    100

Answer

A

Explanation

When two objects start moving towards each other simultaneously from two points and meet, the relation between their speeds s1,s2s_1, s_2 and the times t1,t2t_1, t_2 taken to reach their destinations after meeting is: s1s2=t2t1\frac{s_1}{s_2} = \sqrt{\frac{t_2}{t_1}}

Given s1=60s_1 = 60 km/hr, t1=45t_1 = 45 min, t2=20t_2 = 20 min: 60s2=2045=49=23\frac{60}{s_2} = \sqrt{\frac{20}{45}} = \sqrt{\frac{4}{9}} = \frac{2}{3} s2=60×32=90 km/hrs_2 = 60 \times \frac{3}{2} = 90\text{ km/hr}

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