OCR MEI C2 — Question 2 5 marks

Exam BoardOCR MEI
ModuleC2 (Core Mathematics 2)
Marks5
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TopicGeometric Sequences and Series
TypeFind specific nth term
DifficultyEasy -1.2 This is a straightforward geometric progression question requiring only direct application of standard formulas. Students identify r = 1/2, apply the nth term formula to get (1/2)^19 = 2^(-19), and use the sum to infinity formula S = a/(1-r) = 8. Both parts are routine calculations with no problem-solving or conceptual challenges.
Spec1.04i Geometric sequences: nth term and finite series sum1.04j Sum to infinity: convergent geometric series |r|<1
2 The first three terms of a geometric progression are 4, 2, 1.
Find the twentieth term, expressing your answer as a power of 2 .
Find also the sum to infinity of this progression.
Question 2:
AnswerMarks Guidance
\(a = 4\), \(r = \frac{1}{2}\) identifiedB1 Stated or identified by correct use
\(2^{-17}\)T2 M1 \(20^{\text{th}}\) term \(= \text{their}(a) \times (\text{their } r)^{19}\)
\(8\)S2 M1 \(S = \text{their } (a) \div (1 - \text{their } (r))\)
Total: 5
## Question 2:

$a = 4$, $r = \frac{1}{2}$ identified | B1 | Stated or identified by correct use
$2^{-17}$ | T2 | M1 $20^{\text{th}}$ term $= \text{their}(a) \times (\text{their } r)^{19}$
$8$ | S2 | M1 $S = \text{their } (a) \div (1 - \text{their } (r))$
**Total: 5**

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2 The first three terms of a geometric progression are 4, 2, 1.\\
Find the twentieth term, expressing your answer as a power of 2 .\\
Find also the sum to infinity of this progression.

\hfill \mbox{\textit{OCR MEI C2  Q2 [5]}}
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Q1 5 Q2 5 Q3 5 Q4 11