Time, Speed and Distance Question 4 - CAT 2020
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:
Step-by-Step Explanation
This is a direct application of the Post-Meeting Speed Theorem. When two cars leave opposite ends simultaneously and cross paths, the ratio of their speeds is inversely proportional to the square root of the times taken to reach their final destinations after meeting:
S₁/S₂ = √(t₂/t₁)
We are given S₁ = 60 km/hr, t₁ = 45 minutes, and t₂ = 20 minutes:
60/S₂ = √(20/45) = √(4/9) = 2/3
2 × S₂ = 60 × 3 ⟹ S₂ = 90 km/hr
Correct Option: B
💡 FundaMakers Tip:
Post-meeting travel scenarios are highly predictable. Memorizing the inverse square root identity S₁/S₂ = √(t₂/t₁) bypasses the need to set up intermediate distance variables, turning a multi-stage time-speed-distance problem into a simple 5-second fraction simplification.