| Exam Board | Edexcel |
|---|---|
| Module | C1 (Core Mathematics 1) |
| Marks | 4 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Arithmetic Sequences and Series |
| Type | Sum of specific range of terms |
| Difficulty | Moderate -0.5 This is a straightforward application of the arithmetic series formula requiring students to identify first term, last term, and number of terms, then substitute into the standard formula. It's slightly easier than average as it's a direct single-method question with no problem-solving element, though the non-standard starting index (r=10) adds minor complexity beyond the most routine examples. |
| Spec | 1.04g Sigma notation: for sums of series1.04h Arithmetic sequences: nth term and sum formulae |
| Answer | Marks | Guidance |
|---|---|---|
| AP: \(a = 27\), \(l = 67\) | B1 | |
| \(n = 30 - 9 = 21\) | B1 | |
| \(S_{21} = \frac{21}{2}(27 + 67)\) | M1 | |
| \(= \frac{21}{2} \times 94 = 987\) | A1 | (4 marks) |
AP: $a = 27$, $l = 67$ | B1 |
$n = 30 - 9 = 21$ | B1 |
$S_{21} = \frac{21}{2}(27 + 67)$ | M1 |
$= \frac{21}{2} \times 94 = 987$ | A1 | (4 marks)Evaluate
$$\sum_{r=10}^{30} (7 + 2r).$$ [4]
\hfill \mbox{\textit{Edexcel C1 Q2 [4]}}