Decimals
Add, subtract, multiply and divide decimals.
Worked examples
Adding decimals
Straightforward
Problem
Calculate .
1
Write both numbers with the same number of decimal places.
, so we calculate .
2
Add column by column from right to left.
Hundredths: . Tenths: , write and carry . Ones: .
3
Write the final answer.
Answer
7.28
Multiplying decimals
Moderate
Problem
Calculate .
1
Ignore the decimal points and multiply the whole numbers.
2
Count the total number of decimal places in both original numbers.
has decimal place. has decimal place. Total: decimal places.
3
Place the decimal point in the answer so it has the correct number of decimal places.
Answer
8.4
Dividing decimals with rounding
Challenging
Problem
Calculate , rounding your answer to 2 decimal places.
1
Multiply both numbers by so the divisor becomes a whole number.
2
Perform the division to at least 3 decimal places.
3
Round to 2 decimal places by looking at the third decimal digit.
The third decimal digit is , which is less than , so round down. The second decimal place stays as .
4
Write the final answer.
Answer
5.14
Practise
Q1·Straightforward
Calculate .
Explanation
Add each place value column:
Q2·Straightforward
Calculate .
Explanation
Subtract each place value column:
Q3·Straightforward
Calculate .
Explanation
Align decimal points and add:
Q4·Straightforward
Calculate .
Explanation
Write as and subtract:
Q5·Moderate
Calculate .
Explanation
Ignore the decimal point and multiply: .
has one decimal place, so the answer has one decimal place:
has one decimal place, so the answer has one decimal place:
Q6·Moderate
Calculate .
Explanation
Ignore the decimal points and multiply: .
has one decimal place and has one decimal place, so the answer has two decimal places: .
Simplified:
has one decimal place and has one decimal place, so the answer has two decimal places: .
Simplified:
Q7·Moderate
Calculate .
Explanation
Ignore the decimal points and multiply: .
has one decimal place and has one decimal place, so the answer has two decimal places: .
Simplified:
has one decimal place and has one decimal place, so the answer has two decimal places: .
Simplified:
Q8·Moderate
Calculate .
Explanation
Ignore the decimal points and multiply: .
has one decimal place and has one decimal place, so the answer has two decimal places: .
Simplified:
has one decimal place and has one decimal place, so the answer has two decimal places: .
Simplified:
Q9·Challenging
Calculate .
Explanation
Multiply both numbers by :
Q10·Challenging
Calculate .
Explanation
Multiply both numbers by :
Q11·Challenging
Calculate , rounding your answer to 2 decimal places.
Explanation
Multiply both numbers by :
Perform the division:
The third decimal digit is , so round up:
Perform the division:
The third decimal digit is , so round up:
Q12·Challenging
Calculate , rounding your answer to 2 decimal places.
Explanation
Multiply both numbers by :
Perform the division:
The third decimal digit is , so round up:
Perform the division:
The third decimal digit is , so round up: