1.

A boy walks to his school at a distance of 6 km with constant speed of 2.5 km/h and walks back with a constant speed of 4 km/h. His average speed for the round trip is:

Answer»

`(24)/(13) kmh^(-1)`
`(40)/(13) kmh^(-1)`
3 km/h
`1/2Km h^(-1)`

Solution :`t_1=(6)/(2.5)=(12)/(5)` HR,`t_2=(6)/(4)=(3)/(2)hr`
TOTAL TIME `(t_1+t_2)=(12)/(5)+(3)/(2)=(39)/(10)hr`.
`v_a=(6+6)/((39)/(10))=(40)/(13) km//hr`


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