These invented examples illustrate GCSE skills and show how reasoning can turn a correction into an answer the learner understands.
Maths: why equal percentage changes do not cancel
A price of £50 rises by 20%, then falls by 20%. Saying “back to £50” treats both percentages as a share of the original price. After the increase, the price is £50 × 1.20 = £60. The decrease is now 20% of £60, or £12, so the final price is £48.
A better explanation names the changing starting amount: the second percentage acts on £60. To check understanding, try £80 increased by 15% then decreased by 15%. It becomes £92, then £78.20. Explaining why it finishes below £80 matters as much as the calculation.
English Language: support an inference with the words on the page
Take this invented sentence: “Maya folded the letter twice and pushed it beneath her plate.” Asked what her action might suggest, “Maya is sad” gives an emotion without showing how the sentence supports it.
A more grounded response is: “Maya may want to hide the letter because she pushes it ‘beneath her plate’, putting it out of sight.” This connects a possible meaning to precise evidence without pretending to know her motive for certain. A different interpretation can work if the words support it. Now compare “Maya laid the letter open in the centre of the table”: the new action makes concealment a less convincing reading.
Science: more gas does not necessarily mean a faster reaction
Imagine a reaction has collected 0 cm³ of gas at the start, 40 cm³ after 20 seconds and 60 cm³ after 40 seconds. A pupil might see the larger total and say the reaction is speeding up. Compare equal time intervals instead.
The first interval produces 40 cm³ in 20 seconds: a mean rate of 2 cm³/s. The next produces only 20 cm³ in 20 seconds: 1 cm³/s. The gas total is still rising, but the mean rate has fallen. On a graph of collected gas volume against time, the second interval has a smaller average gradient. If the total reaches 70 cm³ at 60 seconds, the next interval’s mean rate is 10 ÷ 20 = 0.5 cm³/s.