# Write number sentences that involve mixed operations II

Lesson

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.

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.

1. Find $3\times300+70$3×300+70, the amount of water Roald used.