A boy walking at a speed of 15 km/h reaches his school 20

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A boy walking at a speed of 15 km/h reaches his school 20 min late. Next time he increases his speed by 5 km/h but still he late by 5 min. Find the distance of the school from his home.?

1. 5 km
2. 10 km
3. 15 km
4. 20 km

Correct Option: C

Let the distance = x
Here, the difference in time
= 20 - 5 = 15 min
= 15/60 = 1/4h
Speed during next journey
= 15 + 5 = 20 km/h
According to the question,
x/15 - x/20 = 1/4
⇒ 4x - 3x/60 = 1/4
⇒ x = 60/4 = 15
∴ x = 15 km