Overview
This lecture reviews how to add, subtract, multiply, and divide decimals, focusing on correct setup and decimal placement for each operation.
Adding Decimals
- Always line up the decimal points vertically before adding decimals.
- Use placeholder zeros to even out the number of decimal places if needed.
- Add digits from right to left; bring the decimal straight down in the answer.
- Estimation helps check if your answer is reasonable.
Subtracting Decimals
- Line up the decimals and use placeholder zeros for alignment.
- Subtract digits right to left, borrowing as necessary.
- Remember to bring the decimal point straight down into the answer.
- Use estimation to check if the result makes sense.
Multiplying Decimals
- Do not line up decimals; ignore them while multiplying the numbers as whole numbers.
- Count the total decimal places from both factors and include the same number of decimal places in the product.
- Place the decimal in the computed answer according to the total decimal places counted.
- Estimate to confirm if the answer is reasonable.
Dividing Decimals
- Make the divisor (outside number) a whole number by moving the decimal to the right; do the same for the dividend.
- Bring the decimal point straight up from the dividend to the answer line in division.
- Perform long division as with whole numbers, then place the decimal accordingly.
- Check your answer with estimation to verify reasonableness.
Key Terms & Definitions
- Decimal Point — The symbol (.) separating whole numbers from fractional decimal parts.
- Placeholder Zero — A zero added to keep decimal places lined up without changing value.
- Divisor — The number outside the division bracket, what you divide by.
- Dividend — The number inside the division bracket, what is being divided.
Action Items / Next Steps
- Practice adding, subtracting, multiplying, and dividing decimals with attention to decimal placement.
- Refer to additional in-depth videos on each operation if further help is needed.