Standard +0.8 This requires constructing a clear diagram from text description, identifying three specific triangles, then proving their areas match given expressions—demanding spatial reasoning and geometric proof skills beyond routine calculation. However, it's a structured proof with a clear target rather than open-ended problem-solving.
At least one height correctly found and related to diagram
B1
AO 2.2a
Each triangle has area half base times height: \(\frac{(2^2-1^2)}{2}\), \(\frac{(3^2-2^2)}{2}\) and \(\frac{(4^2-3^2)}{2}\)
B1 [3]
AO 2.4. Correct completion (including base \(=1\) either labelled on at least one triangle or stated). Dep on B2
## Question 12:
| Answer | Marks | Guidance |
|--------|-------|----------|
| Correct triangles identified (diagram shown) | B1 | AO 3.2a. Correct triangles identified |
| At least one height correctly found and related to diagram | B1 | AO 2.2a |
| Each triangle has area half base times height: $\frac{(2^2-1^2)}{2}$, $\frac{(3^2-2^2)}{2}$ and $\frac{(4^2-3^2)}{2}$ | B1 [3] | AO 2.4. Correct completion (including base $=1$ either labelled on at least one triangle or stated). Dep on B2 |
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12 With the aid of a suitable diagram, show that the three triangles referred to in line 26 have the areas given in line 27 .
\hfill \mbox{\textit{OCR MEI Paper 3 2023 Q12 [3]}}