# Interview Questions

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# Upstream-Downstream relative speed question

- September 24, 2015
- Posted by: Kamal Rawat
- Category: Quantitative Aptitude

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A person rides a cycle at a constant speed.

When he drives in the direction of the wind, he is able to go 35 km in 5 hrs. While returning, when the wind was against the direction of his driving, he took 7hrs for the same distance.

At what speed does he rides when there is no wind?

**Solution:**

Let speed of cycle = x km/hr.

Let speed of wind = y km/hr.

we know the formulas, Let’s revise them:

While riding in the direction of the wind, speed = x + y

While riding in the opposite direction of the wind, speed = x + y

35 = (x + y) * 5

35 = (x – y) * 7

Elaborating the equations, we get

5.x + 5.y = 35

7.x – 7.y = 35

Solving the above equations:

x = 6, y = 1

Speed of cycle = 6 km/hr.

Speed of Wind = 1 km/hr.