1, the farmer's uncle has a rectangular vegetable field 8 meters long and 5 meters wide, surrounded by fences. How long is the fence? If one side is against the wall, how many meters should the fence be at least?

Solution:

( 1)(8+5)×2

= 13×2

=26 (m)

(2)8+5×2

=8+ 10

= 18 (m)

This fence is 26 meters long. If one side is against the wall, the fence should be at least 18 meters.

2. Enclose a trapezoidal vegetable field with a fence. It is understood that the fence is 35 meters long. How many square meters is the area of vegetable field?

Solution: (35-8)×8÷2

=27×8÷2

=2 16÷2

= 108 (m2)

Answer: The vegetable area is 108 square meters.

3. The school plans to enclose a rectangular biological park with a fence with a length of 16m to raise small animals. One side of the biological park is against the wall (as shown in the figure), with a length of 8m and an area of 30m2, thus finding the length and width of the biological park.

Solution: If the width is xm, then the length is (16-2x) m.

X ( 16-2x) = 30，

Solution: x 1=3, x2=5.

When x=3, 16-2x = 10 > 8 (omitted),

When x=5, 16-2x=6.

A: The width of the biological park is 5 meters and the length is 6 meters.