OCR MEI AS Paper 2 2019 June — Question 3 3 marks

Exam BoardOCR MEI
ModuleAS Paper 2 (AS Paper 2)
Year2019
SessionJune
Marks3
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicIndices and Surds
TypeShow surd expression equals value
DifficultyModerate -0.8 This is a straightforward surd comparison requiring a standard technique (squaring both sides) with minimal steps. The method is commonly taught and practiced, making it easier than average, though it does require knowing to square rather than attempting decimal approximation.
Spec1.01a Proof: structure of mathematical proof and logical steps1.02b Surds: manipulation and rationalising denominators

3 Without using a calculator, prove that \(3 \sqrt { 2 } > 2 \sqrt { 3 }\).

Question 3:
AnswerMarks Guidance
Answer/WorkingMark Guidance
LHS is \((\sqrt{9} \times \sqrt{2}) = \sqrt{18}\)B1 (2.1) OR LHS squared is 18. No calculator. No decimal values allowed.
RHS is \((\sqrt{4} \times \sqrt{3}) = \sqrt{12}\)B1 (1.1) RHS squared is 12
\(\sqrt{18} > \sqrt{12}\) oe (so \(3\sqrt{2} > 2\sqrt{3}\))E1 (2.4) AG. OR e.g. \(\sqrt{3} \times \sqrt{3} \times \sqrt{2} > \sqrt{2} \times \sqrt{2} \times \sqrt{3}\), so \(\sqrt{3} > \sqrt{2}\), which is true. Allow proof that starts with answer and shows it must be true.
[3]
## Question 3:

| Answer/Working | Mark | Guidance |
|---|---|---|
| LHS is $(\sqrt{9} \times \sqrt{2}) = \sqrt{18}$ | B1 (2.1) | OR LHS squared is 18. No calculator. No decimal values allowed. |
| RHS is $(\sqrt{4} \times \sqrt{3}) = \sqrt{12}$ | B1 (1.1) | RHS squared is 12 |
| $\sqrt{18} > \sqrt{12}$ oe (so $3\sqrt{2} > 2\sqrt{3}$) | E1 (2.4) | AG. OR e.g. $\sqrt{3} \times \sqrt{3} \times \sqrt{2} > \sqrt{2} \times \sqrt{2} \times \sqrt{3}$, so $\sqrt{3} > \sqrt{2}$, which is true. Allow proof that starts with answer and shows it must be true. |
| **[3]** | | |
3 Without using a calculator, prove that $3 \sqrt { 2 } > 2 \sqrt { 3 }$.

\hfill \mbox{\textit{OCR MEI AS Paper 2 2019 Q3 [3]}}