Andrew Teoh's answer to liang liang's Secondary 3 E Maths Singapore question.
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This is a tricky question, and there are a few things to take note of:
1. The diagram does not show it, but the model is of a square based pyramid, not a triangle. Therefore, the surface area has to include all four sides as well as the base.
2. After solving the quadratic equation, we reject the solution where x is negative, since 2x represents a real length and hence cannot be negative.
3. The model is a 1:100 scale with the real pyramid, which means 1cm becomes 1m. It is best to convert lengths from the model scale to the real scale before finding area, since a scale of 1:100 would scale 1cm^2 to 10000cm^2.
Hope this helps, and do feel free to ask any clarification questions! :)
1. The diagram does not show it, but the model is of a square based pyramid, not a triangle. Therefore, the surface area has to include all four sides as well as the base.
2. After solving the quadratic equation, we reject the solution where x is negative, since 2x represents a real length and hence cannot be negative.
3. The model is a 1:100 scale with the real pyramid, which means 1cm becomes 1m. It is best to convert lengths from the model scale to the real scale before finding area, since a scale of 1:100 would scale 1cm^2 to 10000cm^2.
Hope this helps, and do feel free to ask any clarification questions! :)
Date Posted:
11 months ago
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