Question

a train travell a distance with speed of 30km and returns with 20km per hour find average speed​

Answer 1

$\huge{\sf{\underline{Answer ;}}}$

$<b>Let s/2 be the Distance Covered by the Train throughout the Whole Journey.$

» With the speed of 30 kmph, it will cover a distance of s/2×30 in t1 hours

So, t1 = s/60

» With the speed of 20 kmph, it will cover a distance of s/2×20 in t2 hours

t2 = s/40

Hence, the average speed = Total distance travelled / total time taken

= d + d / t1 + t2

= 2d / s/60 + s/40

= 2d / 5s/120

= 48 kmph.