AlgebraVery hardGreatest length under a perimeter limit
Algebra practice question
A rectangle has a width of 7 centimetres and a whole-number length. Its perimeter must be at most 40 centimetres. What is the greatest possible length, in centimetres?
Answer: 13
2(l + 7) ≤ 40 gives l ≤ 13.
Common wrong answers
- If you answered 12
- 12 stops one short.
- If you answered 20
- 20 halves 40 without subtracting the width.
- If you answered 26
- 26 uses l + 7 ≤ 40 without the factor 2.
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