1.

A car moving over a straight path, covers a distance d with constant speed of 40 km/hr and then the same distance with speed 60km/hr. The average speed of car is .....

Answer»

50 km/hr
48 km/hr
52 km/hr
None of the given

Solution :To cover DISTANCE d with constant speed 40 km /hr,
Time `t_(1) = (d)/(40) hr.`
And to cover distance d with constant speed 60 km/hr required time `t _(2) = (d)/(60) hr.`
`therefore ` TOTAL time required to cover distance 2D is
`t = t _(1)+t _(2)`
`therefore t = (60 d )/(40) + (d)/(60)`
`therefore t = (60 d + 40 d )/(2400)`
`therefore t = (d)/(24)`
Now average velocity `bar V = (2d)/(t) = 2d xx (24)/(d) = 48 Km//hr`


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