October 2020 Paper 2 Q5
5 The first \(n\) terms of an arithmetic series are
\(17 + 28 + 39 + \ldots + 281 + 292\).
(a) Find the value of \(n\). [1]
(b) Find the sum of these \(n\) terms. [2]
| Scheme | Marks | AO |
|---|---|---|
| 26 | B1 | 1.1 |
| [1] |
Notes
B1: NB \(17 + (n-1) \times 11 = 292\)
| Scheme | Marks | AO |
|---|---|---|
| \(\dfrac{\text{their } 26}{2} \times (17 + 292)\) oe | M1 | 1.1 |
| 4017 | A1 | 1.1 |
| [2] |
Notes
M1: \(\dfrac{\text{their } 26}{2} \times (2 \times 17 + (\text{their } 26 - 1) \times 11)\)