Write number sentences that involve mixed operations II
There are many operations we use in mathematical problems such as add (+), subtract (-), multiply (x) and divide (÷). You have been learning how to solve mathematical problems with one operation.
For example: $2\times3=6$2×3=6
$4+5=9$4+5=9
What happens when there is more than one operation in a mathematical problem. How do we know which operation to calculate first?
For example, how would we solve $6\times5+3\div1$6×5+3÷1?
Unlike reading a book, we don't perform the operations from left to right. There is a special order we use called the order of operations.
Step 1: Do operations inside brackets (...) (also called parentheses)
Step 2: Do multiplication and division going from left to right.
Step 3: Do addition and subtraction going from left to right.
Watch this video to learn how these rules apply to solving mathematical problems.
Worked Examples
Question 1
Evaluate $10+16\div4$10+16÷4.
Question 2
Roald was making tea for $3$3 guests. He filled each cup with $300$300 mL of boiling water. He also spilt $70$70 mL of water onto the kitchen counter. The amount of water Roald used is $3\times300+70$3×300+70.
Find $3\times300+70$3×300+70, the amount of water Roald used.