A bus covers 3 equal distances. The first is covered with speed 10 km/h, second with speed 20 km/h and third with 60 km/h, then find its average speed in km/h.

A bus covers 3 equal distances. The first is covered with speed 10 km/

1.	A bus covers 3 equal distances. The first is covered with speed 10 km/h, second with speed 20 km/h and third with 60 km/h, then find its average speed in km/h.
Answer» 9 16 18 60 Solution :Suppose TOTAL distacne is 3d and distance in each part is d. Time taken to cover `1 ^(STH)` part, `t _(1) = (d)/(10)` Time taken to cover `2^(nd)` pard, `t _(2) = (d)/(20)` Time taken to cover `3^(rd)` part, `t _(3) =(d )/(30)` Total time taken, `t =(3d)/(lt V gt )` `therefore t = t _(1) + t _(2) + t _(3)` `(3d)/(lt v gt) = (d)/(10) + (d)/(20) + (d)/(60)` `therefore(3)/(lt v gt) = (6 + 3 +1)/(60)` `therefore (3)/(lt v gt) = (10)/(60)` `therefore lt v gt = (3 xx 60)/(10)` `therefore lt v gt = (180)/(10)` `therefore lt v gt = 18 km//h`