Adding and Subtracting Whole Numbers
Whole numbers are numbers without fractions or decimals, such as 0, 1, 2, 3, and so on. When adding whole numbers, you combine their values to get a bigger number. For example, 3 + 4 = 7. When subtracting, you find out how many more one number is compared to another, like 7 - 4 = 3.
Tips for Adding and Subtracting:
- Line up numbers by place value (ones under ones, tens under tens, etc.).
- Start adding or subtracting from the rightmost digit (ones place) and move left.
- Regroup or borrow when necessary (e.g., if a digit in the top number is smaller than the bottom one).
Place Value
Place value tells you the value of a digit based on its position in a number. For example, in the number 345:
- The digit 5 is in the ones place (value = 5).
- The digit 4 is in the tens place (value = 40).
- The digit 3 is in the hundreds place (value = 300).
Understanding place value is important because it helps you add and subtract numbers correctly, especially when dealing with regrouping.
Rounding Whole Numbers
Rounding means finding the closest number to a given value based on a specific place value to make numbers simpler or easier to work with. Here's how to round a number:
- Identify the place you want to round to (ones, tens, hundreds, etc.).
- Look at the digit immediately to the right of that place.
- If this digit is 5 or greater, increase the rounding digit by 1.
- If this digit is less than 5, keep the rounding digit the same.
- Change all digits to the right of the rounding place to zero.
Example: Round 346 to the nearest ten.
- Look at the tens place: 4.
- Look to the right digit (ones place): 6.
- Since 6 ≥ 5, increase the tens digit (4) by 1 → 5.
- Change the ones place to 0.
- Rounded number = 350.
Summary
- Addition and Subtraction: Combine or remove quantities, lined up by place value.
- Place Value: The value of a digit based on its position.
- Rounding: Making numbers simpler by adjusting to the nearest specified place value.