Multiple choice

In the following questions, two equations Quantity I and Quantity II are given. You have to solve both the equations and give answer. $I-A man can row a distance of 4km upstream in 30 min and returns the same distance in 20 min. How much time will he take to row the same distance in downstream if due to a wind the speed of the current gets doubled?$ $II-A 200 meter long train crosses a 600 meter long bridge in 20 seconds. What time will it take to cross a platform 480 meter long?$

  1. Quantity I > Quantity II

  2. Quantity I ≥ Quantity II

  3. Quantity II > Quantity I

  4. Quantity II ≥ Quantity I

  5. Quantity I = Quantity II or Relation cannot be established
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A Correct answer
Explanation

Quantity I: Upstream speed = 4km/(0.5hr) = 8km/h, downstream = 4km/(1/3hr) = 12km/h. Boat speed = (8+12)/2 = 10km/h, current = 2km/h. If current doubles to 4km/h, new downstream = 14km/h, time = 4/14hr = 17.14min. Quantity II: Total distance = 200+600 = 800m in 20s, so speed = 40m/s. For 480m platform, distance = 200+480 = 680m, time = 680/40 = 17s. Since 17.14 > 17, Quantity I > Quantity II.

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