Grade 5 Mathematics
When adding or subtracting decimals, the #1 RULE is:
LINE UP THE DECIMAL POINTS!
This ensures you add tenths to tenths, hundredths to hundredths, and so on. You can add zeros as placeholders to help!
Find: 5.7 + 3.45
Step 1: Line up decimals
Step 2: Add zero, then add
Adding zeros doesn't change the value! 5.7 = 5.70 = 5.700. The zeros help us line up the places correctly.
Find: 8.3 - 4.68
Step 1: Line up & add zero
Step 2: Regroup & subtract
Hundredths: Can't do 0 - 8, so borrow from tenths. 10 - 8 = 2
Tenths: Now we have 2 tenths (3-1=2). Can't do 2 - 6, so borrow from ones. 12 - 6 = 6
Ones: Now we have 7 ones (8-1=7). 7 - 4 = 3
WRONG: Some students line up the last digits: 5.7 + 3.45 as 57 + 345. This gives a wrong answer!
RIGHT: Always line up the decimal points first! Then add zeros if needed to make the same number of decimal places.
1. Find: 4.6 + 2.83
Answer:
2. Find: 9.5 - 3.72
Answer:
3. Find: 12 - 5.38
Answer:
4. Maria bought a notebook for $3.75 and a pen for $1.50. How much did she spend in total?
Answer: $