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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?
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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