A farmer has 80 m of fencing to enclose a rectangular field along a straight river. No fence is needed along the river. Find the largest area A that can be enclosed.
Optimization worksheet with answers
A rectangular pen is fenced with 72 m of fencing and divided into two parts by one extra fence parallel to the sides of length x (three fences of length x and two of length y in total). Find the largest total area A that can be enclosed.
A closed cylindrical can (with a top and a bottom) must hold 500 cm³. The metal used is proportional to the total surface area. Find the radius r that uses the least material.
An open box (no lid) with a square base must hold 32000 cm³. Use the least possible material, that is the smallest area of the base plus the four sides. Find the height h.
A small firm sells its product at a fixed market price of €70 per unit. Producing q units costs C(q) = 1100 + 10q + 0.5q² euros. Find the maximum profit P.
A company sells q units per week. The price at which it can sell them is p = 180 − 1q euros per unit, and the cost is C(q) = 2700 + 15q euros. Find the price p that maximises profit.
Answer key
- 1. A = 800 m²
- 2. A = 216 m²
- 3. r = 4.301 cm
- 4. h = 20 cm
- 5. P = 700 €
- 6. p = 97.5 €
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