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.