Money · percentages
Bag a bargain!
🎓 School maths · Years 5–7Percentages — Find a percentage of an amount (a discount) and work out the new price.Maths by year →
The Case. The trainers you want are £40 — but there's 25% off! What do you actually pay? Working out discounts is money maths you'll use your whole life.
Your tools. numpy does the percentage sums on every item at once; matplotlib shows what you save.
Investigate. Press Run. Each item shows its full price and the sale price — plus your total saving.
- Change the discounts and watch your savings grow.
- This is exactly the maths behind every shop's sale.
your_code.py
Starting Python…
The Reveal
Starting Python… (first time only — a few seconds)
🗒️ Detective's notes
Bundles your findings, chart and code into one PDF you can keep, print or hand in.
🧩 How this code works
The tools it uses
- NumPy — a row of boxes that holds numbers, so you can do maths to all of them at once.
- Matplotlib — your crayon box — it turns numbers into charts and pictures.
What this one does
- • It draws a bar chart — great for comparing amounts.
How to read it, top to bottom
- 1. Import — bring in the tools (listed above).
- 2. The data — the lists and numbers near the top. These are the bits you change.
- 3. The work — a little maths, or a loop that repeats a step.
- 4. Show it —
print(...)writes words;plt.show()draws the picture.
Use it for your own problems
- Change the numbers at the top and press Run — nothing breaks, so experiment!
- Ask your own version of the question — swap in your family, your scores, your week.
- The same tools work on any numbers — that's the superpower you're learning.
Need a hint?
25% off means you pay 75% — that's price * (1 - 25/100). Percentages are just parts out of 100.