a boy run for 10min at uniform speed of 9km/h.at what speed should. he run for next 20min .so that the average speed comes 12km/h?
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Okay we'll be solving it in two parts
Part 1-
Boy travels @ 9km/hr for 10 minutes that means he covers 1.5km in 10 minutes.
Part 2-
What speed should he travel for the next 20 minutes so that his average speed comes out to be 12km/hr.
12km/hr could means that a boy should travels 6 km in 30 minutes. So that means our whole distance comes out to be of 6km.
But the boy already had travel 1.5km in his first 10 minutes so for the next 20 minutes his distance will be 6-1.5= 4.5km for 20minutes in order to achieve an avg. speed of 12km/h.
Now we have got d(=4.5km)
t(=20minutes or 1/3hour)
so the average speed for the next 20 minutes= distance/time= 4.5*3= 13.5km/h.
Part 1-
Boy travels @ 9km/hr for 10 minutes that means he covers 1.5km in 10 minutes.
Part 2-
What speed should he travel for the next 20 minutes so that his average speed comes out to be 12km/hr.
12km/hr could means that a boy should travels 6 km in 30 minutes. So that means our whole distance comes out to be of 6km.
But the boy already had travel 1.5km in his first 10 minutes so for the next 20 minutes his distance will be 6-1.5= 4.5km for 20minutes in order to achieve an avg. speed of 12km/h.
Now we have got d(=4.5km)
t(=20minutes or 1/3hour)
so the average speed for the next 20 minutes= distance/time= 4.5*3= 13.5km/h.
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