3 mistakes that quietly lose the most marks in Foundation maths (and the 30-second fix for each)
The same handful of mistakes come up every single paper and they're not hard topics, they're just habits nobody corrected. If you fix these three before your next paper you'll pick up marks. No new content to learn, just unlearning.
- Adding fractions straight across
1/2 + 1/3 = 2/5, right? It's the most natural-looking thing in the world. AQA's own examiner reports say more than half of Foundation students do this on every paper.
The fix: a fraction is one number, not two. The bottom (denominator) names the size of the slice; the top counts how many. You can't add them until the slices are the same size. Common denominator first, then add the tops only: 3/6 + 2/6 = 5/6. The bottom never gets added.
- Doing percentage change by adding/subtracting the percent
"15% off £80" → people do 80 − 15 = 65, or chain two changes by adding the percentages. Both wrong.
The fix: use a multiplier. 15% off = ×0.85. 15% on = ×1.15. £80 × 0.85 = £68. Want to reverse a price that already had 20% added? You divide by 1.2, you don't take 20% off. Anchor everything on the original amount and multiply.
- Mixing up area and perimeter
The trap is assuming a bigger perimeter means a bigger area (it doesn't), or using radius where you needed diameter.
The fix: different dimensions, different rules. Perimeter is 1-D: you add lengths. Area is 2-D: you multiply two lengths. If your area answer is in cm and not cm², you've made this mistake.