Grade 5 Mathematics
Dividing decimals works just like dividing whole numbers - but you need to watch the decimal point!
There are TWO main types:
1. Dividing a decimal BY a whole number (like 8.4 / 2)
2. Dividing BY a decimal (like 12 / 0.3)
9.6 / 4 = ?
Set up the division just like with whole numbers. Put the decimal point in the quotient directly above where it is in the dividend.
The decimal point goes straight up!
Check with estimation: 9.6 is close to 10. 10 / 4 = 2.5. Our answer of 2.4 is close to 2.5. It makes sense!
15 / 0.5 = ?
Make the divisor a whole number. Move the decimal in 0.5 one place to the right. 0.5 becomes 5.
Move the decimal in the dividend the SAME amount. Move the decimal in 15 one place right. 15 becomes 150.
15 / 0.5
Move both decimals 1 place right
150 / 5 = 30
Check: Does 30 make sense? How many halves (0.5) are in 15? Since 0.5 is half, there are TWICE as many halves as wholes. 15 x 2 = 30. Yes!
WRONG THINKING: "Division always makes numbers smaller, so 15 / 0.5 should be less than 15."
RIGHT THINKING: When you divide by a number LESS than 1, the answer is BIGGER than what you started with! Think: "How many 0.5s fit into 15?" More than 15 of them fit!
Before solving, estimate to know if your answer makes sense:
1. 8.4 / 2 =
Estimate first: 8 / 2 = ______, so my answer should be close to ______
2. 15.5 / 5 =
Show your work:
3. 12 / 0.4 =
Step 1: Make 0.4 a whole number: 0.4 becomes ______
Step 2: Move the decimal in 12 the same way: 12 becomes ______
Step 3: Divide: ______ / ______ = ______
4. Maria has 7.2 meters of ribbon. She wants to cut it into pieces that are each 0.9 meters long. How many pieces can she make?
Equation: ______ / ______ = ______
Answer: Maria can make ______ pieces.