## 243. Math Puzzle $8 / 85$

In a section of a steelworks, there is a small and a large Siemens-Martin furnace. The larger one produces three times as much as the smaller one. Together, they melt a certain amount of steel in one week.

In how many days can each of the furnaces produce this amount of steel on its own?
The smaller Siemens-Martin furnace produces $1 / 4$ of the daily output, the larger one $3 / 4$; in 7 days, therefore, $7 / 4$ and 21/4, respectively, together 28/4.

The smaller one thus needs 28 days, the other $\frac{28}{4}: \frac{3}{4}=9 \frac{1}{3}$ days $=9$ days 8 hours.