Two boys start running at the same time in the same direction at a speed of 10 km/hr and 12 km/hr respectively. In what time they will be 8 km apart?A)6hrsB)5hrsC)4hrsD)3hrs
Question
Two boys start running at the same time in the same direction at a speed of 10 km/hr and 12 km/hr respectively. In what time they will be 8 km apart?A)6hrsB)5hrsC)4hrsD)3hrs
Solution 1
The problem can be solved by using the concept of relative speed.
Step 1: Calculate the relative speed. The boys are running in the same direction, so their relative speed will be the difference of their speeds, which is 12 km/hr - 10 km/hr = 2 km/hr.
Step 2: Calculate the time taken to be 8 km apart. The formula to calculate time is distance/speed. Here, the distance is 8 km and the relative speed is 2 km/hr. So, the time taken will be 8 km / 2 km/hr = 4 hours.
So, the answer is C) 4 hours.
Solution 2
The problem can be solved by using the concept of relative speed.
Step 1: Calculate the relative speed. The boys are running in the same direction, so their relative speed will be the difference of their speeds, which is 12 km/hr - 10 km/hr = 2 km/hr.
Step 2: Calculate the time it takes for them to be 8 km apart. The formula to calculate time is distance/speed. Here, the distance is 8 km and the relative speed is 2 km/hr. So, the time it will take for them to be 8 km apart is 8 km / 2 km/hr = 4 hours.
So, the answer is C) 4 hours.
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