1. The teacher cut a square sheet of paper with a side of 5 cm into two rectangles. The perimeter of one of these rectangles is $16 \mathrm{cm}$. What is the perimeter of the other?
1. The first method of solving.
1) $16: 2=8$ cm - the semi-perimeter of the first rectangle;
2) $8-5=3$ cm - the width of the first rectangle;
3) $5-3=2$ cm - the width of the second rectangle;
4) $(2+5) \times 2=14 \text{cm} -$ the perimeter of the second rectangle.

The second method of solving. Before solving by the second method, it is necessary to make a drawing.

1) $16: 2=8$ cm - the semi-perimeter of the first rectangle;
2) $8-5=3$ cm - the width of the first rectangle;
3) $5 \times 4=20$ cm - the perimeter of the square;
4) $3 \times 2=6$ cm - the doubled width of the first rectangle;
5) $20-6=14$ cm - the perimeter of the second rectangle.

Answer: 14 cm.