In a race, the average speed of a runner is 10 km/h. If he runs for 2 hours and then increases his speed to 15 km/h for the next 3 hours, what is his average speed for the entire race?
Practice Questions
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Q1
In a race, the average speed of a runner is 10 km/h. If he runs for 2 hours and then increases his speed to 15 km/h for the next 3 hours, what is his average speed for the entire race?
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Total distance = (10 * 2) + (15 * 3) = 20 + 45 = 65 km. Total time = 2 + 3 = 5 hours. Average speed = 65 / 5 = 13 km/h.
Questions & Step-by-step Solutions
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Q
Q: In a race, the average speed of a runner is 10 km/h. If he runs for 2 hours and then increases his speed to 15 km/h for the next 3 hours, what is his average speed for the entire race?
Solution: Total distance = (10 * 2) + (15 * 3) = 20 + 45 = 65 km. Total time = 2 + 3 = 5 hours. Average speed = 65 / 5 = 13 km/h.
Steps: 5
Step 1: Calculate the distance covered in the first part of the race. The runner's speed is 10 km/h and he runs for 2 hours. So, distance = speed * time = 10 km/h * 2 hours = 20 km.
Step 2: Calculate the distance covered in the second part of the race. The runner's speed is 15 km/h and he runs for 3 hours. So, distance = speed * time = 15 km/h * 3 hours = 45 km.
Step 3: Add the distances from both parts of the race to find the total distance. Total distance = 20 km + 45 km = 65 km.
Step 4: Calculate the total time taken for the race. The total time = time for first part + time for second part = 2 hours + 3 hours = 5 hours.
Step 5: Calculate the average speed for the entire race. Average speed = total distance / total time = 65 km / 5 hours = 13 km/h.
