Adding and Subtracting Decimal Numbers and Whole Numbers
Add and subtract decimals and whole numbers in Grade 6 math by aligning decimal points in a column, using zeros as placeholders, and computing just as with whole numbers.
Key Concepts
New Concept Squaring a number means multiplying the number by itself. Finding the square root of a number is the inverse of squaring a number.
"Seven squared" is $7 \times 7$, which is 49. $$7^2 = 49$$ The principal square root of 81 is 9. $$\sqrt{144} = 12$$ What’s next This is your introduction to these foundational concepts. Soon, we'll apply them in worked examples and challenge problems involving area, perimeter, and order of operations.
Common Questions
How do you add decimal numbers?
Write the numbers vertically with decimal points aligned. Add zeros as placeholders so both numbers have the same number of decimal places. Then add column by column from right to left, just like whole numbers.
How do you subtract decimal numbers?
Align decimal points vertically, add zeros as needed, then subtract from right to left with borrowing as necessary. The decimal point in the answer goes directly below the decimal points in the problem.
Why is aligning decimal points important?
Aligning decimals ensures you add or subtract digits with the same place value (tenths with tenths, hundredths with hundredths). Misaligning decimal points is the most common source of errors in decimal arithmetic.
How do you add or subtract a decimal and a whole number?
Write the whole number with a decimal point and zeros after it. For example, 5 becomes 5.000. Then align the decimals and compute normally. The decimal point stays in the same position in the answer.