O-LevelAdditional MathematicsSeries4037/12 · Oct/Nov 2025 · Q36 Marks
The sum of the first two terms of a geometric progression is 9. The sum to infinity of this geometric progression is 25.
- (a)Find the possible values of the common ratio of this geometric progression.[4]
- (b)Find the first term of this geometric progression for each possible value of the common ratio.[2]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2025). The mark or mark type is shown in brackets.
- [4] B1 a+ar=9 or a(1-r²)/(1-r) = 9 or a(r²-1)/(r-1) = 9
- B1 a/(1-r) = 25
- B1 Dep B mark on both previous B marks for r² = 16/25
- B1 Dep B1 mark on all previous B marks for r=±4/5 or ±0.8
- [2] B1 for each a = 5, 45
Write your answer and get it marked
On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.
Sign up free →