## 248. Math Puzzle $1 / 86$

To dig a trench for an underground line, two excavators are available. The smaller one would dig the trench alone in 10 days, the larger one in 8 days.

Together, they would have managed it in a bit more than 4 days. However, due to a repair, the larger excavator had to pause for one day.

When will the trench be finished?
From the given information, the following solution scheme is derived:

$$
\frac{x}{8}-\frac{1}{8}+\frac{x}{10}=1 \quad, \quad \frac{5 x-5+4 x}{40}=1 ; \quad x=5
$$

If the large excavator is not in use for one day, the trench will be completed in five days.