Question

A train goes from Gandhinagar to Patna at a speed of 128 kmph and returns to Gandhinagar at a different speed. If the average speed for the entire journey is l 12 kmph, then find the speed of the train for the return journey (to nearest kmph)

पर्याय

• 96 kmph

• 192 kmph

• 48 kmph

• None of these

Answer 1

None of these

Explanation:

We know Average Speed = `"total distance"/"total time"`

In case distance is same then we can use the SHORT CUT METHOD

Average speed = `(2xy)/(x + y)` ......(where x, y are speed)

⇒ 112 = `(2 xx 128 xx y)/(128 + y)`

⇒ 14336 + 112 y = 256 y

⇒ y = 99.99 or 100 kmph