If Edwin can drop a piece of luggage and record the results once every 5 minutes, we can begin by calculating the total time it would take for him to drop and record results 18 times.
Given that each drop and recording takes 5 minutes, we can calculate the total time \( T \):
\[ T = \text{Number of drops} \times \text{Time per drop} \]
\[ T = 18 \times 5 = 90 \text{ minutes} \]
Since Edwin and Hewitt are working together, they will be recording the drops simultaneously. Each can drop luggage and record results every 5 minutes.
If both Edwin and Hewitt are working together, the number of drops they can achieve in the same amount of time increases.
If both Edwin and Hewitt drop luggage at the same time, they can perform a total of 2 drops every 5 minutes.
To determine how many drops they need to make to reach the combined total of 18 drops:
\[ \text{Total drops needed} = 18 \] \[ \text{Number of drops per 5 minutes} = 2 \]
Now, we can calculate how many 5-minute intervals are needed to achieve 18 drops:
\[ \text{Intervals needed} = \frac{\text{Total drops}}{\text{Drops per interval}} = \frac{18}{2} = 9 \text{ intervals} \]
Since each interval is 5 minutes, the total time taken would be:
\[ \text{Total time} = \text{Intervals needed} \times \text{Time per interval} = 9 \times 5 = 45 \text{ minutes} \]
Therefore, it will take Edwin and Hewitt together a total of 45 minutes to drop their luggage and record the results a combined total of 18 times.