Adding and subtracting decimals is just whole-number adding once the decimal points are lined up. That runs on reading place value (tenths, hundredths) and solid whole-number addition and subtraction. Warm these up and decimal math lines up neatly.
Answer these 3, then press Show my path. No grade — this just points you to the right level.
1. In 3.7, what digit is in the tenths place?
2. What is 46 + 27?
3. What is 80 − 35?
To add or subtract decimals, stack the numbers so the decimal points line up — that keeps tenths over tenths and hundredths over hundredths. Then add or subtract like whole numbers and drop the point straight down.
Your quick check picks one for you, but you can switch any time:
Level 0 Let's warm up whole-number adding and place value.
A. What is 5 + 3?
5 + 3 = 8.
B. What is 9 − 4?
9 − 4 = 5.
C. In 6.2, the digit 2 is in the ___ place.
The first digit right of the point is the tenths place.
Level 1 Now add and subtract simple decimals.
A. What is 1.2 + 1.5?
2 tenths + 5 tenths = 7 tenths; 1 + 1 = 2. Answer 2.7.
B. What is 3.6 − 1.4?
6 tenths − 4 tenths = 2 tenths; 3 − 1 = 2. Answer 2.2.
Level 2 Warm-up straight into decimal sums with regrouping.
A. What is 2.7 + 1.5?
7 tenths + 5 tenths = 12 tenths = 1.2; carry 1: 2 + 1 + 1 = 4. Answer 4.2.
B. What is 5.3 − 2.8?
Borrow: 13 tenths − 8 tenths = 5 tenths; 4 − 2 = 2. Answer 2.5.
1. What is 4.5 + 2.3?
5 tenths + 3 tenths = 8 tenths; 4 + 2 = 6. Answer 6.8.
2. What is 7.6 − 3.2?
6 tenths − 2 tenths = 4 tenths; 7 − 3 = 4. Answer 4.4.
You've practiced exactly what Lesson 1-5 uses. Time to dive in.
Start Lesson 1-5 →