Problem
Add: 12.45 + 3.8
📝Step-by-Step Solution
1
Write the numbers vertically
Stack the numbers on top of each other, making sure to line up the decimal points.
12.45
+ 3.80
2
Add placeholder zeros
Add zeros to make the decimal parts the same length: 3.8 becomes 3.80. This doesn't change the value.
3.8 = 3.80
3
Add from right to left
Hundredths: 5 + 0 = 5. Tenths: 4 + 8 = 12 (write 2, carry 1). Ones: 2 + 3 + 1 = 6. Tens: 1 + 0 = 1.
4
Bring down the decimal point
The decimal point in the answer goes directly below the decimal points above.
12.45 + 3.80 = 16.25
✅Final Answer
16.25
The key to adding decimals is alignment! Always line up the decimal points, then add as you would with whole numbers. Adding zeros as placeholders helps keep columns aligned. The decimal point in your answer goes straight down.
Ready to Practice Decimals?
Generate a personalized practice test with MathQuizily. Get instant PDF downloads with answer keys.