Problem 4. Petar walked $1 \mathrm{~km}$ from his house to his friend's house. With the distance he walked, he could circle his grandfather's garden, which has a rectangular shape, 25 times. Determine the length and width of the garden, if they differ by $4 \mathrm{~m}$.
Solution. The perimeter of the garden is $1000: 25=40 \mathrm{~m}$. Let the length be denoted by $a$, and the width by $b$. We have: $a+b=20$ and $a-b=4$. By adding the equations, we get $2a=24$, from which $a=12 \mathrm{~m}$, and thus $b=8 \mathrm{~m}$.

## V section