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Question
Neelaveni goes by bicycle to her school every day. Her average speed is 12 km/hr and she reaches school in 20 minutes. What is the increase in speed, If she reaches the school in 15 minutes?
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Solution
Let the speed to reach school in 15 min be x
| Speed in Km/hr | 12 | x |
| Time in min | 20 | 15 |
∴ They are in inverse proportion
x1y1 = x2 y2
12 × 20 = x × 15
x = `(12 xx 20)/15`
x = 16
If she reaches in 15 min the speed = 16 km/hr
Already running with 12 km/hr
∴ Increased speed = 16 – 12 = 4 km/hr
Increase in speed = 4 km/hr
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