The diagram shows a rectangular sheet of glass. By writing each measurement correct to \(1\) significant figure, estimate the area of the sheet of glass.
Question 1 Report
The diagram shows a rectangular sheet of glass.
By writing each measurement correct to \(1\) significant figure, estimate the area of the sheet of glass.
Answer Details
An estimate question asks you to round first and then calculate, so that the arithmetic can be done mentally. Correct to \(1\) significant figure the two measurements of the rectangular sheet become \(7\) cm and \(4\) cm.
\[\text{Area}\approx 7\times 4\] [M1]
\[=28\ \text{cm}^{2}\] [A1]
The area of a rectangle is length \(\times\) width, and multiplying centimetres by centimetres gives square centimetres, so the unit must be cm\(^{2}\).
Two things lose marks here: working out the exact area with a calculator and then rounding the answer (the rounding must come first, and the question says to write each measurement to \(1\) significant figure), and giving the perimeter instead of the area. Estimation is being tested as a check on calculator work, so the rounded values should be visible in the working.
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