Higher January 2020 Paper 2R Q22
22 The first term of an arithmetic series \(S\) is −6
The sum of the first 30 terms of \(S\) is 2865
Find the 9th term of \(S\).
(4)
| Scheme | Marks |
|---|---|
| (2865 =) \(\dfrac{30}{2}(2 \times -6 + 29d)\) | M1 |
| \(d = 7\) | A1 |
| \(-6 + 8 \times \text{“}7\text{”}\) or (\(n\)th term =) \(-6 + \text{“}7\text{”}(n - 1)\) | M1 |
| 50 | A1 |
| (4) | |
| (4 marks) |
Notes
M1: Correct expression for sum of 30 terms
A1: Correct value for \(d\)
M1: ft their \(d\). Dep on M1