A rectangular rooftop garden EFGH has 30 solar lights placed at equal distances along sides EF, FG and GH. A light is placed at each corner, and the distance between adjacent lights is 8 m. The breadth EF is 56 m. What is the length FG of the garden?
Need a hint?
Count the gaps between the first and last lights, and remember that the breadth is used twice.
Worked answer
- The 30 lights create 30 − 1 = 29 equal gaps.
- Total distance along EF, FG and GH = 29 × 8 = 232 m.
- The two breadth sides measure 2 × 56 = 112 m in total.
- FG = 232 − 112 = 120 m.
Answer: 120 m
The mistake this question tests
Habit
Area and perimeter formulas
A pupil may count 30 equal gaps instead of 29, forgetting that the number of gaps between 30 lights is one fewer than the number of lights.
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