The answer
\(11.6\%\) (3 s.f.)
O-Level E-Math 2025 Paper 1 Question 14 · Verified worked solution by the Genius Plus Academy teaching team
What this question tests
This is Question 14 of the O-Level E-Math 2025 Paper 1. It tests successive percentage change, in the Percentage area. It is worth 3 marks. It is a worded / diagram-based question, so open your Ten-Year Series (TYS) or the official paper at this question, then follow our full worked solution below.
Take the 2018 GNI as 100. By 2021 it is \(100 \times 1.0924 = 109.24\). Apply the yearly changes to reach 2020: \(2019 = 100 \times 1.0363 = 103.63\); \(2020 = 103.63 \times (1 - 0.0556) = 103.63 \times 0.9444 = 97.8682\).
Let the increase from 2020 to 2021 be \(p\%\). Then \(97.8682 \times \left(1 + \dfrac{p}{100}\right) = 109.24\), so \(1 + \dfrac{p}{100} = \dfrac{109.24}{97.8682} = 1.11622\ldots\), giving \(p = 11.6\%\) (3 s.f.).
Answer: \(11.6\%\) (3 s.f.)
Same structure, different numbers
Swap the constants, dress a quadratic as a length, hide a derivative inside an integral, and a student sees a brand new problem. The structure underneath is the same, and so is the method. Once a student can name the structure, a whole row of questions that look different start to open the same way.
That is where marks really leak: in choosing the method, not in the algebra that follows. We call it Lock and Key, name the lock, then the key follows.
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Genius Plus Academy · O-Level & IP Mathematics
Our O-Level E-Math tuition trains the same recognise-the-structure method these worked solutions show, taught by a team that has marked these papers for years. It runs within our weekly Secondary Math programme, Sec 1 to 4 and IP.
It is a successive percentage change question from Percentage, worth 3 marks.
Yes. IP (Integrated Programme) schools teach the same O-Level Mathematics content; they just sequence it differently and set their own internal exams, so these worked solutions apply to IP students too.
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