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A person goes from point S to T and comes back. His average speed for the whole journey is 70 km/hr. If his speed while coming back from T to S is 80 km/hr, then what will be the speed of the person (in km/hr) while going from S to T?

A person goes from point S to T and comes back. His average speed for the whole journey is 70 km/hr. If his speed while coming back from T to S is 80 km/hr, then what will be the speed of the person (in km/hr) while going from S to T? Correct Answer 62.22

We know that,

If ‘x’ km/hr is the speed from A to B and ‘y’ km/hr is the speed from B to A then,

Average speed = 2xy/(x + y)

⇒ 70 = (2 × x × 80)/(x + 80)

⇒ 35(x + 80) = 80x

⇒ 45x = 35 × 80

⇒ x = 62.22 km/hr

∴ The speed of the person while coming back from S to T = 62.22 km/hr

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