# 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

Question 26 Mean Median And Mode Of Ungrouped Data Exercise 18A

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.

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.

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