1-2 Adding and Subtracting Decimals What You’ll Learn To add and subtract decimals

Add Decimals: No Regrouping Adding two decimal numbers with more than one digit is very similar to adding whole numbers. At this level, problems are presented in vertical format with the decimal points lined up correctly. There is no regrouping, carrying, borrowing, or trading involved in this skill.

Add Decimals A decimal number is a number that uses place value and a decimal point to show tenths, hundredths, thousandths, etc. For example, the number 3.57 has a 5 in the tenths place and a 7 in the hundredths place. The difference between adding decimals and adding whole numbers is the fact that the decimal points must be lined up before addition can occur.

Example 1: Solve Step 1: Add the tenths column (3 + 4 = 7). Write 7 in the tenths column (below the line). Step 2: Bring down the decimal point. Step 3: Add the ones column (2 + 1 = 3). Write 3 to the left of the decimal point to finish the problem.

Add Decimals: Regrouping Adding two decimal numbers with regrouping is very similar to adding whole numbers with regrouping. These problems are presented in a vertical format with the decimal points lined up correctly. These problems require regrouping, carrying, or trading.

Example 2: Solve = ? Step 1: Write the problem vertically. Make sure the decimal points are lined up. Step 2: Add one zero to 2.4 so that the two numbers have the same number of digits. Step 3: Add the hundredths column (0 + 8 = 8). Write the 8 in the hundredths column (below the line). Step 4: Add the tenths column (4 + 6 = 10). Write the 0 in the tenths column (below the line) and carry the 1 to the ones column (left of the decimal point). Step 5: Bring the decimal point straight down. Step 6: Add the ones column, including the 1 that was carried ( = 4). Place the 4 to the left of the decimal point to finish the problem

Subtract Decimals: No Regrouping Subtracting two decimal numbers with more than one digit is very similar to subtracting whole numbers. These problems are presented in vertical format with the decimal points lined up correctly. There is no regrouping, carrying, borrowing, or trading involved in this skill.

Example 3: = ? Step 1: Make sure the decimal points are lined up. Step 2: Subtract the hundredths column (6 - 2 = 4). Write 4 in the hundredths column. Step 3: Subtract the tenths column (5 - 1 = 4). Write 4 in the tenths column. Step 4: Bring down the decimal point. Step 5: Subtract the whole numbers (2 - 1 = 1). Write 1 to the left of the decimal point to finish the problem

Subtract Decimals: Regrouping Subtracting two decimal numbers with more than one digit is very similar to subtracting whole numbers. These problems are presented in a vertical format with the decimal points lined up correctly. These problems require regrouping, carrying, or trading.

Example 1: Solve = ? Step 1: Make sure the decimal points are lined up. Step 2: Begin with the hundredths column (two places to the right of the decimal point). Regrouping must occur because you cannot subtract 5 from 0. Borrow 1 whole from the next column, changing the 4 to a 3. Give the 1 to the hundredths column, creating 10. Subtract the hundredths column ( = 5). Put the 5 in the hundredths column below the line. Step 3: Subtract the tenths column. Regrouping must occur because you cannot subtract 8 from 3. Borrow 1 whole from the ones column (one place to the left of the decimal point), changing the 3 to a 2. Give the 1 to the tenths column. Subtract the tenths column ( = 5). Put the 5 in the tenths column below the line. Step 4: Bring down the decimal point. Step 5: Subtract the ones column (2 - 0 = 0). Put the 2 to the left of the decimal point (below the line) to finish the problem Example 4: Solve = ?