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JJ.1 Round to the nearest ten

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What does it mean to round numbers?

Rounding is a way to make a number simpler while keeping its value close to the original number. We use rounding to help estimate or work with numbers more easily.

Examples:
  • 47 rounded to the nearest ten → 50
  • 82 rounded to the nearest ten → 80
  • 134 rounded to the nearest ten → 130
Note

When you round, the number changes but stays close to the original value.

Rules for rounding to the nearest ten

To round to the nearest ten, look at the digit in the ones place. That digit tells you whether to round up or round down.

Steps:
  • Look at the ones digit.
  • If the ones digit is 0–4, keep the tens digit the same and change the ones digit to 0.
  • If the ones digit is 5–9, add 1 to the tens digit and change the ones digit to 0.
Note

Always check the ones place to decide whether to round up or down.

Examples of rounding numbers

Let’s practice rounding different numbers to the nearest ten using the rules.

Examples:
  • 76 → Ones digit is 6, so round up → 80
  • 243 → Ones digit is 3, so round down → 240
  • 159 → Ones digit is 9, so round up → 160
Note

Circle the ones digit when working on paper. This will help you see if the number rounds up or down.

Why do we round numbers?

We round numbers to make them easier to use in math. Rounding helps us estimate quickly, especially when adding, subtracting, or solving real-world problems.

Examples:
  • Rounding 198 to 200 makes adding easier: 200 + 50 = 250 (close to the exact answer 248).
  • If a book costs $27, rounding to 30 helps you quickly estimate the total cost when buying several books.
Note

Estimates do not give exact answers, but they are very useful for checking if an answer makes sense.