Money Moves: Budgets, Percentages and Interest

You need: a spending diary template (real, or for a persona) · calculator · coloured pencils

1. For one week, record every spend: date, item, cost and whether it was a need or a want. Use a persona if you prefer to keep your own spending private.
2. Group the spends into categories (food, transport, phone, fun, gifts, saving).
3. Calculate each category as a fraction, decimal and percentage of the week's total.
4. Draw a bar graph and a percentage bar, and circle any leaks: small spends that add up.

How you'll know: Your percentages add to 100% (allowing for rounding), and you can name one change that would free up money for saving.

Go further: Multiply your biggest leak by 52. What could that yearly amount buy instead?

You need: supermarket, hardware or clothing catalogues · calculator · recording table

1. Find five items with a 'was' and 'now' price. Work out the discount in dollars, then as a percentage of the original price.
2. Find a percentage-off deal and work out the new price two ways: subtract the discount, and multiply by the percentage you still pay.
3. Compare '30% off', 'buy two, get one free' and '$20 off when you spend $100' for the same shopping list.
4. Round cash totals to the nearest 10 cents and work out the change from $50.

How you'll know: Your two methods give the same price, and you can explain which deal is best for your list and why.

Go further: 'Buy two, get one free' is the same as what percentage off, if you actually want three? What if you only want one?

You need: prices and sizes for five products in two pack sizes (catalogue, online or a shop visit) · calculator

1. For each product, divide the price by the size to find the price per 100 g, per litre or per item.
2. Compare the two sizes. Record which is cheaper and by what percentage.
3. Check whether the shelf label's unit price matches your calculation.
4. Decide when the cheaper-per-unit pack is still not the best choice (it goes off, it costs too much at once, you won't use it all).

How you'll know: Your unit prices are correct to the nearest cent, and you found at least one case where the bigger pack was not cheaper.

Go further: Build a ratio table for a market-day recipe and find the cheapest way to buy ingredients for 60 muffins.

You need: a recipe or product list · ingredient prices · calculator · a cash float of coins and notes (supervised)

1. Work out the total cost of one batch, then the cost per item.
2. Decide a price and calculate the profit per item and the profit as a percentage of the cost.
3. Predict sales and total profit. Plan a cash float so you can give change.
4. On the day, record every sale. Give change correctly, rounding cash totals to the nearest 10 cents.
5. Afterwards, compare actual profit with the prediction and explain the difference.

How you'll know: Your records balance: float + takings − change given = cash in the tin, and the profit percentage is calculated from real numbers.

Safety: Follow the school's food-safety rules: clean hands and surfaces, covered food, and every item labelled with its allergens (nuts, eggs, dairy, gluten). Two people count cash together.

Go further: Try a price experiment: sell at one price for the first half hour and a lower price for the second. Which earned more profit?

You need: three or four real NZ phone plans (prepay 28-day, prepay monthly, on-account) · calculator · graph paper or Desmos

1. Record each plan's price, period, data and minutes.
2. Find the yearly cost. A 28-day plan renews 13 times a year (52 ÷ 4 = 13), not 12.
3. Add a handset: bought outright, or paid monthly over 24 months. Find the two-year total for each combination.
4. Graph total cost against months for each plan and find where the lines cross.
5. Recommend a plan for a light, a medium and a heavy data user.

How you'll know: Your yearly totals are correct, the 28-day trap is spotted, and each recommendation is backed by a number.

Go further: Work out the cost per gigabyte of data for each plan. Does the cheapest plan give the cheapest data?

You need: a real 'pay later' terms page or the Sorted guide · calculator

1. Take a $240 purchase split into four fortnightly payments of $60. What is the total if every payment is on time?
2. Add a late fee (use the real fee from the terms page) for one missed payment, then two. Work out the extra cost as a percentage of $240.
3. Compare with saving $30 a week and buying the item in eight weeks.
4. Write the advice you would give an older sibling in two sentences.

How you'll know: You can show the percentage extra that late fees add, and explain what makes 'pay later' risky even when it says 'no interest'.

Go further: Four items bought on 'pay later' in the same month: build a calendar of every payment due. What happens to a $60-a-week budget?

You need: today's savings rates from two or three NZ banks · calculator or spreadsheet

1. Use I = P × r × t to find the interest on $500 at each bank's rate for 1, 3 and 5 years.
2. Race two savers: one saves $10 a week from today, the other $20 a week starting in six months. Make a table of their totals each month for a year.
3. Find when the second saver catches up, if they do.
4. Graph both savers and describe the shape of each line.

How you'll know: Your interest calculations are correct, and you can explain with numbers why starting earlier matters.

Go further: Compound interest: add the interest to the balance each year. Compare simple and compound interest on $500 at 4% after 10 years, and test the 'rule of 72' (72 ÷ rate ≈ years to double).

You need: a list of costs for the event (food, venue, travel, koha or gifts) · calculator · today's exchange rate if travelling overseas

1. List and estimate every cost, then add 10% for surprises.
2. Share costs between households in a fair ratio (for example by number of people, 2 : 3 : 5).
3. If the trip is overseas, convert costs using today's exchange rate (for example, if NZ$1 buys about 1.6 Sāmoan tālā, 400 tālā is about NZ$250).
4. Make a weekly savings plan that reaches each household's share on time.

How you'll know: Every share adds up to the total, the currency conversions are sensible when you estimate them, and the savings plan reaches the goal by the date.

Go further: What if the exchange rate changes by 5% before you travel? Recalculate and decide how much buffer to keep.