Date | May 2022 | Marks available | 1 | Reference code | 22M.1.SL.TZ2.2 |
Level | Standard Level | Paper | Paper 1 (without calculator) | Time zone | Time zone 2 |
Command term | State | Question number | 2 | Adapted from | N/A |
Question
The nth term of an arithmetic sequence is given by un=15-3n.
State the value of the first term, u1.
Given that the nth term of this sequence is -33, find the value of n.
Find the common difference, d.
Markscheme
u1=12 A1
[1 mark]
15-3n=-33 (A1)
n=16 A1
[2 marks]
valid approach to find d (M1)
u2-u1=9-12 OR recognize gradient is −3 OR attempts to solve -33=12+15d
d=-3 A1
[2 marks]
Examiners report
A large majority of candidates earned full marks for this question. In part (a), a surprising number of candidates did not substitute n=1 into the given expression, erroneously stating u1=15. Many of these candidates were able to earn follow-through marks in later parts of the question. In part (b), algebraic errors led a few candidates to find inappropriate values for n, such as n=-6.