5. Marko wants to install a shelf in his room. The boards for the shelf can be arranged in 4 or 5 rows, but their total area must be exactly $1 \mathrm{~m}^{2}$. In the store, he found boards that are $125 \mathrm{~cm}$ long. How many boards and what width should he buy for his shelf?

Problems worth 10 points:
First method:

The total area of all the planks must be $10000 \mathrm{~cm}^{2}$. 1 POINT

If he wants a shelf with 4 rows, the area of each plank is $2500 \mathrm{~cm}^{2}$.

If the length of the plank is $125 \mathrm{~cm}$, the width must be $2500: 125=20 \mathrm{~cm}$. 2 POINTS

If he wants a shelf with 5 rows, the area of each plank needs to be $2000 \mathrm{~cm}^{2}$.

The width is then $2000: 125=16 \mathrm{~cm}$.

2 POINTS

Marko needs to buy 4 planks that are $20 \mathrm{~cm}$ wide or 5 planks that are $16 \mathrm{~cm}$ wide.

1 POINT

TOTAL 6 POINTS