How to Round to the Nearest Ten
Rounding to the nearest ten means finding the closest multiple of 10 to a given number. The key digit to examine is the ones digit (the last digit of the whole number part).
The Rounding Rule
To round to the nearest ten:
- Look at the ones digit (the digit in the ones place).
- If the ones digit is 5 or greater (5, 6, 7, 8, 9), round up to the next ten.
- If the ones digit is less than 5 (0, 1, 2, 3, 4), round down to the current ten.
- Replace the ones digit with 0.
Examples
347 rounds to 350
The ones digit is 7, which is 5 or greater, so we round up.
342 rounds to 340
The ones digit is 2, which is less than 5, so we round down.
345 rounds to 350
The ones digit is exactly 5, so by convention we round up.
95 rounds to 100
The ones digit is 5, round up. 9 in the tens place carries over to 100.
Practical Applications
- Mental math: Rounding to the nearest ten simplifies quick calculations in your head.
- Estimation: Quickly estimate sums, differences, and totals by rounding to tens first.
- Classroom learning: Rounding to the nearest ten is one of the first rounding concepts taught in elementary school.
- Inventory: Businesses often round quantities to the nearest ten for ordering.
- Scoring: Some scoring systems round to the nearest ten for simplicity.
Rounding Decimals to the Nearest Ten
When rounding a decimal number to the nearest ten, first consider the whole number part. The ones digit still determines the rounding direction. For example, 73.8 has a ones digit of 3, so it rounds down to 70. The decimal portion does not affect rounding to the nearest ten.
Tips for Accurate Rounding
- Always identify the ones digit before making your decision.
- The ones digit and everything to its right becomes zero after rounding.
- Watch for carry-over cases where rounding up changes multiple digits (e.g., 95 to 100).
- For negative numbers, the same rule applies to the absolute value.