Tens & Ones
Place value in tens and ones forms the foundation of the decimal number system, where each digit's position determines its value. In any two-digit number, the left digit represents tens (groups of 10) and the right digit represents ones (individual units). For example, in the number 47, the digit 4 represents 40 (4 tens) and the digit 7 represents 7 ones.
Why it matters
Understanding tens and ones enables children to work with money, as 10 pence coins and 1 penny pieces mirror this place value system directly. When counting classroom resources like pencils in boxes of 10, or calculating bus fares using 10p and 1p coins, this concept proves essential. The skill underpins addition and subtraction algorithms taught in Year 3, where regrouping 10 ones into 1 ten becomes crucial for calculations like 47 + 26. Shopping scenarios frequently require breaking down prices — understanding that £23 contains 2 tens (£20) and 3 ones (£3) helps with mental arithmetic. Later mathematical concepts including multiplication by 10, decimal place value, and percentage calculations all depend on this foundational understanding of how position affects digit value.
How to solve tens & ones
Place Value — Tens & Ones
- In a two-digit number, the left digit = tens, the right digit = ones.
- 34 = 3 tens + 4 ones = 30 + 4.
- The value of a digit depends on its position.
- Hundreds are to the left of tens: 245 = 2 hundreds + 4 tens + 5 ones.
Example: In 72: the 7 is worth 70 (7 tens), the 2 is worth 2 (2 ones).
Worked examples
Count by tens: 30, 40, 50, __
Answer: 60
- Find the pattern → Each number is 10 more than the last — Look at the gaps: 30 to 40 is +10, 40 to 50 is +10. The pattern is adding 10 each time.
- Add 10 to the last number: 50 + 10 → 60 — 50 + 10 = 60. When counting by tens, the ones digit stays at 0 and the tens digit goes up by 1.
I have 8 dimes and 4 pennies. How much money do I have in cents?
Answer: 84
- Count the dimes: 8 × 10 → 80 — Each dime is worth 10 cents. With 8 of them: 8 × 10 = 80.
- Add the pennies: 4 × 1 → 80 + 4 = 84 — Add the pennies: 80 + 4 = 84 cents total. This is just like place value — tens and ones!
Write 25 in expanded form.
Answer: 20 + 5
- Break 25 into its place values → 25 = 2 tens + 5 ones — The digit 2 is in the tens place, the digit 5 is in the ones place. Expanded form shows what each digit is really worth.
- Write each digit's value → 20 + 5 — 2 tens = 20. 5 ones = 5. Expanded form: 20 + 5. This shows exactly how the number is built!
Common mistakes
- Confusing the digit with its value, such as saying the 3 in 34 is worth 3 instead of 30
- Writing expanded form incorrectly, like expressing 56 as 5 + 6 rather than 50 + 6
- Misreading place values in larger numbers, claiming the 4 in 142 represents 4 tens instead of 4 tens (not 4 ones)