A train travels the first 15 km at a uniform speed of $30 k m / h$ ; the next $75 k m$ at a uniform speed of $50 k r n / h$ ; and the last $10 k m$ at a uniform speed of $20 k m / h$ . Calculate the average speed for the entire train journey.

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Solution

Given,
$d_{1} = 15 k m, v_{1} = 30 k m / h$
$d_{2} = 75 k m, v_{2} = 50 k m / h$
$d_{3} = 10 k m, v_{3} = 20 k m / h$

we know that,
average speed $= t o t a l d i s t a n c e c o v e r e d / t o t a l t i m e t a k e n$

total distance covered $= D = 15 + 75 + 10 = 100 k m$

total time taken $= T = (15 / 30) + (75 / 50) + (10 / 20) = 2.5 h o u r s$

so, average speed $= 100 / 2.5 = 40 k m / h$

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A train travels the first 15 km at a uniform speed of 30km/h; the next 75km at a uniform speed of 50krn/h; and the last 10km at a uniform speed of 20km/h. Calculate the average speed for the entire train journey.

Given,d1=15km,v1=30km/hd2=75km,v2=50km/hd3=10km,v3=20km/hwe know that, average speed =total distance covered/total time taken total distance covered =D=15+75+10=100km total time taken =T=(15/30)+(75/50)+(10/20)=2.5hoursso, average speed =100/2.5=40km/h

A train travels the first 15 km at a uniform speed of $30 k m / h$ ; the next $75 k m$ at a uniform speed of $50 k r n / h$ ; and the last $10 k m$ at a uniform speed of $20 k m / h$ . Calculate the average speed for the entire train journey.