| Exam Board | OCR MEI |
|---|---|
| Module | C2 (Core Mathematics 2) |
| Year | 2012 |
| Session | January |
| Marks | 5 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Geometric Sequences and Series |
| Type | Form and solve quadratic in parameter |
| Difficulty | Moderate -0.8 This is a straightforward geometric progression question requiring only standard recall: using the property that b² = 32 × 12.5 to find the middle term, then calculating r and applying the sum formula. The quadratic is simple (perfect square) and all steps are routine textbook exercises with no problem-solving insight needed. |
| Spec | 1.04i Geometric sequences: nth term and finite series sum |
A geometric progression has a positive common ratio. Its first three terms are 32, $b$ and 12.5.
Find the value of $b$ and find also the sum of the first 15 terms of the progression. [5]9 A geometric progression has a positive common ratio. Its first three terms are 32, $b$ and 12.5.\\
Find the value of $b$ and find also the sum of the first 15 terms of the progression.
\hfill \mbox{\textit{OCR MEI C2 2012 Q9 [5]}}