A ship sails out to an island at the rate of 15 km/hr and sails back to the starting point at 10 km/hr. Find

the average sailing speed for the whole journey.

Question

A ship sails out to an island at the rate of 15 kmhr and sails back to the starting point at 10 kmhr Find the average sailing speed for the whole journey

Accepted Answer

Consider x km as the distance of mark from the starting point

So the time taken by the ship to reach the mark = x/15 hours

We know that

The time taken by the ship to reach the starting point from the mark = x/10 hours

So we get

Total time taken = x/15 + x/10

By taking LCM

Total time taken = x/6 hours

We know that total distance covered = x + x = 2x km

So the average sailing speed for the whole journey = 2x ÷ x/6

It can be written as

Average sailing speed for the whole journey = (2x × 6)/ x

So we get

Average sailing speed for the whole journey = 12 km/hr

Therefore, the average sailing speed for the whole journey is 12 km/hr.

RS Aggarwal Solutions Class 9 Mathematics Solutions for Mean Median And Mode Of Ungrouped Data Exercise 18A in Chapter 18 - Mean Median And Mode Of Ungrouped Data