Maths
How does money maths work?
Quick answer
Money maths means counting coins and notes, adding up prices and working out change. Most currencies split one unit into 100 smaller ones, like 100 pence in a pound.
In one sentence
Money math means counting coins and bills, adding up prices and working out change. One dollar is split into 100 cents, so $1 = 100¢.
Explained
Coins and bills
| US coin | Value |
|---|---|
| penny | 1¢ |
| nickel | 5¢ |
| dime | 10¢ |
| quarter | 25¢ |
Paper money comes in bills (called notes in the UK) such as $1, $5, $10 and $20. A price like $4.75 means 4 dollars and 75 cents. The two digits after the point are always the cents, which is why money is where most children first meet decimals.
Pounds and pence. Most currencies split one big unit into 100 small ones. In the UK, £1 = 100 pence (p), and the coins are 1p, 2p, 5p, 10p, 20p, 50p, £1 and £2. The euro has 100 cents, and the Nigerian naira has 100 kobo.
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Counting coins
Start with the biggest coin and count on. A quarter, two dimes, a nickel and three pennies: "25, 35, 45, 50, 51, 52, 53." That's 53¢.
Adding prices
Adding prices is ordinary addition: add dollars and cents separately, or line up the decimal points. $2.45 + $1.30: dollars 2 + 1 = 3, cents 45 + 30 = 75, so $3.75. If the cents reach 100, trade 100¢ for $1.
Making change
Count up from the price to the amount paid. It is easier than subtracting. Worked example: a drink costs $1.35 and you pay with $2.
- $1.35 → $1.40 is 5¢.
- $1.40 → $1.50 is 10¢.
- $1.50 → $2.00 is 50¢.
- Change: 5¢ + 10¢ + 50¢ = 65¢.
Older children use money for percentages too: a 20% discount, or finding which pack is better value by working out the price of one item.
Examples
- 3 quarters + 2 dimes = 75¢ + 20¢ = 95¢
- 125¢ = $1.25
- $10 − $6.49 = $3.51
- Best buy: 4 apples for $1.20 (30¢ each) beats 6 for $2.10 (35¢ each).
- £2.50 = 250p
Common mistakes
- Writing $3.5 for three dollars and fifty cents. This is the most common slip. It is $3.50, with two digits for the cents.
- Judging coins by size or number. A dime is smaller than a nickel but worth twice as much, and five pennies are worth less than one dime.
- Mixing up $0.05 and $0.50. 5¢ and 50¢ are very different amounts.
Quick quiz
Money
Check what you know with 5 quick questions.
Question 1 of 5
How many pence are in £1?
Practise it
Try it
- How much are 2 quarters, 1 dime and 4 pennies?
- A book costs $3.60. You pay with a $5 bill. How much change do you get?
- How many pennies make $2.75?
Answers: 1) 64¢. 2) $1.40 (count up: 40¢ to $4, then $1 to $5). 3) 275.
Money math worksheets
Practise it step by step in a full course: Grade 3 Maths
For grown-ups
Related topics
Decimals
Decimals are numbers with a decimal point. Digits after the point show tenths, hundredths and so on, so 2.5 means two and five tenths.
Addition
Addition is putting amounts together to find a total. The sign is +, and the answer is called the sum or total, so 4 + 3 = 7.
Subtraction
Subtraction is taking one amount away from another, or finding the difference between two numbers. The sign is −, so 9 − 4 = 5.
Percentages
A percentage is a number out of 100, written with the sign %. So 25% means 25 out of every 100, which is the same as one quarter.
The 24-hour clock
The 24-hour clock counts the hours from 00:00 at midnight to 23:59, so there is no am or pm. For afternoon times, add 12: 3 pm is 15:00.
Profit and loss
Profit = selling price − cost price; loss = cost price − selling price. Profit percentage = profit ÷ cost price × 100. Buy at $20, sell at $25: profit $5, which is 25%.