Advanced MathHardLonger side from perimeter and area
Advanced Math practice question
A rectangle has a perimeter of 30 centimetres and an area of 56 square centimetres. What is the length, in centimetres, of its longer side?
Answer: 8
Half the perimeter is 15, so the sides are w and 15 − w. Then w(15 − w) = 56, w² − 15w + 56 = (w − 7)(w − 8) = 0. The sides are 7 and 8; the longer is 8.
Common wrong answers
- If you answered 7
- 7 is the shorter side.
- If you answered 15
- 15 is the sum of the two sides, not a side.
- If you answered 56
- 56 is the area.
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