A spare part is demanded infrequently, with the average time between demands being $6$ weeks. Previous analysis has shown that the time between demands follows a negative exponential distribution.

Simulate the next inter$-$arrival times, using the following stream of random numbers, starting at the leftmost number, and using four$-$digit random numbers:

$9042074505$

If a part has just been demanded, what is your simulated arrival time for the demand for the next part?

Step $3$

Now, let's sum up these interarrival times:

Total simulated time $=$ Interarrival time ${?}_1+$ Interarrival time ${?}_2+$ Interarrival time $3$

Total simulated time ~~$0\mathrm{.}2283+1\mathrm{.}3863+3\mathrm{.}2189$

Total simulated time ~~$4\mathrm{.}8335$ weeks

Explanation:

Since this total simulated time is less than $6$ weeks, the arrival time for the demand of the next part is indeed $4\mathrm{.}8335$ weeks, which rounded to one decimal place is $4\mathrm{.}8$ weeks, or equivalently, $4\mathrm{.}8$ weeks $+0\mathrm{.}3$ weeks $=14\mathrm{.}1$ weeks.

Above is expert's answerk

Why $4\mathrm{.}8+0\mathrm{.}3=14\mathrm{.}1$ weeks???