Advanced MathHardLonger side of a rectangle from its area and perimeter
Advanced Math practice question
A rectangular field has an area of 300 square metres and a perimeter of 70 metres. What is the length, in metres, of its longer side?
Answer: 20
l + w = 35 and lw = 300, so l and w are the roots of t² − 35t + 300 = 0 = (t − 20)(t − 15). The longer side is 20.
Common wrong answers
- If you answered 15
- 15 is the shorter side.
- If you answered 30
- 30 comes from 300 ÷ 10, guessing a width of 10.
- If you answered 35
- 35 is l + w, half the perimeter.
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