Higher January 2019 Paper 2R Q23
23 The 10th term of an arithmetic series, \(S\), is 66
The sum of the first 20 terms of \(S\) is 1290
Find the 5th term of \(S\).
Show your working clearly.
(4)
| Scheme | Marks |
|---|---|
| \(a + 9d = 66\) oe | M1 |
| \(\dfrac{20}{2}(2a + 19d) = 1290\) oe | M1 |
| \(a = 93\) or \(d = -3\) | A1 |
| 81 | A1 |
| (4) | |
| (4 marks) |
Notes
M1: A correct formula involving 10th term
M1: Correct formula for sum of first 20 terms
A1: A correct value for \(a\) or \(d\)
A1: dep on M2