| Exam Board | Edexcel |
|---|---|
| Module | C2 (Core Mathematics 2) |
| Marks | 4 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Geometric Sequences and Series |
| Type | Find sum to infinity |
| Difficulty | Easy -1.2 This is a straightforward geometric series question requiring only basic recall and simple arithmetic. Part (a) involves dividing two terms to find r = -1/5, and part (b) applies the standard sum to infinity formula S = a/(1-r). Both are direct applications of memorized formulas with no problem-solving or conceptual challenge. |
| Spec | 1.04i Geometric sequences: nth term and finite series sum1.04j Sum to infinity: convergent geometric series |r|<1 |
| Answer | Marks | Guidance |
|---|---|---|
| \(r = \frac{-15}{-75} = -\frac{1}{5}\) | M1 A1 | |
| \(= \frac{75}{1-(-\frac{1}{5})} = 62\frac{1}{2}\) | M1 A1 | (4) |
$r = \frac{-15}{-75} = -\frac{1}{5}$ | M1 A1 |
$= \frac{75}{1-(-\frac{1}{5})} = 62\frac{1}{2}$ | M1 A1 | (4)A geometric series has first term 75 and second term $-15$.
\begin{enumerate}[label=(\alph*)]
\item Find the common ratio of the series. [2]
\item Find the sum to infinity of the series. [2]
\end{enumerate}
\hfill \mbox{\textit{Edexcel C2 Q1 [4]}}