Chapter 4.8, Problem 15P

To determine

The average speed for the rest of the trip to maintain the schedule

Answer to Problem 15P

The speed for the rest 6 hours journey should be $26\text{knots}$ .

Explanation of Solution

Given information:

A ship averages 22 knots (nautical miles per hour) to make its 10-hour run on schedule.

During the first four hours bad weather caused to reduce speed to $16\text{knots}$ .

Speed of the ship is $22\text{knots}$ .

Time taken is $10\text{h}$

Total distance is given by,

  $\text{Distance = speed}\times \text{time}$

So, distance travelled by ship is 22(10) $=220\text{km}$

For the first 4 hours,

Speed of the ship is 16 knots

Distance travelled is

  $\text{Distance = speed}\times \text{time}$

  $=16(4)$

  $=64\text{km}$

Distance left for the rest of the journey:

  $220-64$

  $=156\text{km}$

Let the speed to be increased to travel this distance be $x$ knots,

  $\begin{array}{l}\text{Speed}=\frac{\text{distance}}{\text{time}}\\ 16+x=\frac{156}{6}\\ x=26-16\\ x=10\text{knots}\end{array}$

Hence the speed for the rest 6hours journey should be:

  $16+10=26\text{knots}$