Doing money sums in the right order
When a money sum has more than one operation, we must follow the correct order of operations. If we work from left to right without thinking, we may get the wrong answer.
Key idea
1) Do work inside brackets ( ) first.
2) Then do × and ÷, from left to right.
3) Last, do + and −, from left to right.
A worked money example
Ravi buys 3 books at RM7 each and 1 ruler at RM4. How much does he pay?
Worked example
Sum: RM7 × 3 + RM4
Multiply first: RM7 × 3 = RM21
Then add: RM21 + RM4 = RM25
Now try with brackets: (RM6 + RM4) × 2. Do the bracket first: RM6 + RM4 = RM10, then RM10 × 2 = RM20. The brackets change what we do first.
Remember
- Multiply and divide before you add or subtract.
- Always finish the brackets first.
- Check your answer makes sense for real shopping.