A man covers first half of the distance with a speed of 30 km /hr and the remaining distance with a speed of 70 km /hr .Find the Average speed of the Man in the entire Journey?
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let total distance be x
according to question x / 2 distance cover in time t1 ,so
x / 2 = 30*t1 ...............(1)
x / 2 distance cover in time t2 ,so
x / 2 = 70*t2.................(2)
average speed = total distance / total time
= x / t ( where t = t1 + t2)
multiply by 7 / 3 in equation (1)
7x / 6 = 70*t1..................(3)
add equation (2) and (3) we get ,
10x / 6 = (t1 + t2)*70
x / (t1 + t2) = 42
hence average speed = 42 Km / hr
according to question x / 2 distance cover in time t1 ,so
x / 2 = 30*t1 ...............(1)
x / 2 distance cover in time t2 ,so
x / 2 = 70*t2.................(2)
average speed = total distance / total time
= x / t ( where t = t1 + t2)
multiply by 7 / 3 in equation (1)
7x / 6 = 70*t1..................(3)
add equation (2) and (3) we get ,
10x / 6 = (t1 + t2)*70
x / (t1 + t2) = 42
hence average speed = 42 Km / hr
Anonymous:
we can use the shortcut formula , when body travels equal distances with different velocities the average velocity is given by 2*(product of velocities) / sum of velocities
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