A-LevelMathematicsSeries9709/12 · Oct/Nov 2020 · Q45 Marks
The sum, Sₙ, of the first n terms of an arithmetic progression is given by Sₙ = n² + 4n. The kth term in the progression is greater than 200. Find the smallest possible value of k.
- (a)The sum, Sₙ, of the first n terms of an arithmetic progression is given by Sₙ = n² + 4n. The kth term in the progression is greater than 200. Find the smallest possible value of k.[5]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2020). The mark or mark type is shown in brackets.
- [M1] Using two values of n in the given formula
- [A1] a = 5, d = 2
- [M1] Correct formula used with their a and d to form an equation or inequality with 200, condone use of n
- [A1] (k =) 99 Condone ≥ 99
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