OCR MEI C1 — Question 5 4 marks

Exam BoardOCR MEI
ModuleC1 (Core Mathematics 1)
Marks4
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicSolving quadratics and applications
TypeRearranging formula - variable appears multiple times
DifficultyStandard +0.3 This is a straightforward algebraic manipulation requiring students to clear fractions and rearrange to isolate u. While it involves multiple steps (finding common denominator, cross-multiplying, factoring), these are standard C1 techniques with no conceptual difficulty or problem-solving insight required—slightly easier than average.
Spec1.02k Simplify rational expressions: factorising, cancelling, algebraic division
5 Make \(u\) the subject of the formula $$\frac { 1 } { v } - \frac { 1 } { u } = \frac { 1 } { f }$$
Question 5:
AnswerMarks Guidance
\(\frac{1}{v}-\frac{1}{u}=\frac{1}{f} \Rightarrow \frac{1}{u}=\frac{1}{v}-\frac{1}{f}=\frac{f-v}{vf}\)M1 Isolating \(v\)
M1Dealing with fractions
A1Correct expression
\(\Rightarrow u=\frac{vf}{f-v}\)M1 Taking reciprocals
Total: 4
## Question 5:
$\frac{1}{v}-\frac{1}{u}=\frac{1}{f} \Rightarrow \frac{1}{u}=\frac{1}{v}-\frac{1}{f}=\frac{f-v}{vf}$ | M1 | Isolating $v$
| M1 | Dealing with fractions
| A1 | Correct expression
$\Rightarrow u=\frac{vf}{f-v}$ | M1 | Taking reciprocals
**Total: 4**

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5 Make $u$ the subject of the formula

$$\frac { 1 } { v } - \frac { 1 } { u } = \frac { 1 } { f }$$

\hfill \mbox{\textit{OCR MEI C1  Q5 [4]}}
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Q1 2 Q2 3 Q3 4 Q4 4 Q5 4 Q6 4 Q7 5 Q8 5 Q9 5 Q10 12 Q11 12 Q12 12