a train moves with a speed of 30 km/hr in the first 15 min, with another speed of 40 km/hr in the next 15 min and then with a speed of 60 km/hr in the last 30 min. calculate the average speed of the train for this journey.

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Solution

x1 = v1 x t1 = 30 x (15/60) = 7.5 km
x2 = v2 x t2 = 40 x (15/60) = 10 km
x3 = v3 x t3 = 60 x (30/60) = 30 km
now,
X = x1 + x2 + x3 = 7.5km + 10km + 30km = 47.5km
and
T = t1 + t2 + t3 = 15min + 15min + 20min = 1hr
so,
v_av = X / T = 47.5km /1hr
thus,
v_av = 47.5 km/hr

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a train moves with a speed of 30 km/hr in the first 15 min, with another speed of 40 km/hr in the next 15 min and then with a speed of 60 km/hr in the last 30 min. calculate the average speed of the train for this journey.

x1 = v1 x t1 = 30 x (15/60) = 7.5 kmx2 = v2 x t2 = 40 x (15/60) = 10 kmx3 = v3 x t3 = 60 x (30/60) = 30 kmnow,X = x1 + x2 + x3 = 7.5km + 10km + 30km = 47.5kmandT = t1 + t2 + t3 = 15min + 15min + 20min = 1hrso,vav = X / T = 47.5km /1hrthus,vav = 47.5 km/hr

x1 = v1 x t1 = 30 x (15/60) = 7.5 km
x2 = v2 x t2 = 40 x (15/60) = 10 km
x3 = v3 x t3 = 60 x (30/60) = 30 km
now,
X = x1 + x2 + x3 = 7.5km + 10km + 30km = 47.5km
and
T = t1 + t2 + t3 = 15min + 15min + 20min = 1hr
so,
v_av = X / T = 47.5km /1hr
thus,
v_av = 47.5 km/hr