Line up the decimal points, then add or subtract just like whole numbers. Use this every time you work with money.
When you add or subtract decimals, line up the decimal points first. Then add zeros if needed so every number has the same number of decimal places, and calculate column by column.
1. You buy a sandwich for $3.40 and a drink for $1.25. How much do you spend in total? (Type the number, e.g. 4.65)
Line up: 3.40 + 1.25. Hundredths: 0 + 5 = 5. Tenths: 4 + 2 = 6. Ones: 3 + 1 = 4. Total = 4.65.
2. You pay $10.00 for a book that costs $6.75. How much change do you get back?
10.00 − 6.75. Borrow to get: 10.00 − 6.75 = 3.25.
3. Calculate: $2.50 + $3.75
2.50 + 3.75 = 6.25.
4. Calculate: $10.00 − $4.65
10.00 − 4.65 = 5.35.
5. Which symbol makes it true? (1.8 + 0.45) ___ 2.3
1.80 + 0.45: hundredths 0 + 5 = 5, tenths 8 + 4 = 12 → write 2, carry 1, ones 1 + 0 + 1 = 2. Result = 2.25. Compare 2.25 to 2.30: the tenths are equal (2), but hundredths 2 < 3, so 2.25 < 2.30.
6. Three friends split the cost of supplies. Anya spends $4.50, Ben spends $3.25, and Cara spends $2.10. How much did they spend altogether?
4.50 + 3.25 = 7.75. Then 7.75 + 2.10 = 9.85.
7. You have $20.00. You buy items costing $8.47. How much money do you have left?
20.00 − 8.47. Borrow as needed: 20.00 − 8.47 = 11.53.