Advanced MathEasyArea of a pen from a quadratic model
Advanced Math practice question
A rectangular pen is built with 20 metres of fencing. If its width is w metres, its area A, in square metres, is given by A(w) = w(10 − w). What is the area when w = 4?
Answer: 24
A(4) = 4(10 − 4) = 4 × 6 = 24.
Common wrong answers
- If you answered 6
- 6 is the length, 10 − 4, not the area.
- If you answered 16
- 16 is 4², not 4 × 6.
- If you answered 40
- 40 is 4 × 10, forgetting to subtract the width.
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