SSC Test Questions A car covers 4 successive 3km stretches at speed of 10kmph, 20kmph, 30kmph & 60kmph resp. Its average speed is ?

SSC Test Questions A car covers 4 successive 3km stretches at speed

1.	SSC Test Questions A car covers 4 successive 3km stretches at speed of 10kmph, 20kmph, 30kmph & 60kmph resp. Its average speed is ?
Answer» The average speed of car is 20kmphStep-by-step EXPLANATION:We KNOW,Average speed = ( Total distance ) / ( Total Time )Firstly, We calculate the total time taken by car :Time = Distance / SpeedTime taken when travelling at a speed of 10 kmph:Speed = 10 km/hrDistance = 3 kmTime = 3 / 10 hrTime taken when travelling at a speed of 20 kmph:Speed = 20 km/hrDistance = 3 kmTime = 3 / 20 hrTime taken when travelling at a speed of 30 kmph:Speed = 30 km/hrDistance = 3 kmTime = 3 / 30 = 1 / 10 hrTime taken when travelling at a speed of 60 kmph:Speed = 60 km/hrDistance = 3 kmTime = 3 / 60 = 1 / 20 hrTotal time:T = 3/10 + 3/20 + 1/10 + 1/20 = ( 6 + 3 + 2 + 1 ) / 20= 12 / 20 = 3 / 5 hourTotal distance:D = 3 * 4 = 12 kmAverage speed = ( Total distance ) / ( Total time )Substituting the values,Speed = 12 / ( 3 / 5 )Speed = ( 12 * 5 ) / 3= 60 / 3=20 kmphHence,The average speed of car is 20kmph