Write equations from word problems

A word problem can be represented by an equation that names the quantities, preserves their relationships, and uses a symbol or letter for an unknown number. This includes one- and two-step whole-number situations involving addition, subtraction, multiplication, or division, with the unknown potentially representing a result, a starting quantity, a change, or a group size; the equal sign indicates that both sides have the same value, not merely that an answer follows.

Detailed Explanation: Write equations from word problems

An equation is a math sentence that shows two amounts are equal. Use a letter, such as $n$ , for the unknown number.

Example

There are $3$ boxes with $8$ crayons in each box. Then $7$ crayons are used. How many crayons are left?

1. Find the important quantities.

$3$ boxes
$8$ crayons in each box
$7$ crayons used
The number of crayons left is unknown

2. Choose a letter for the unknown.

Let $n$ represent the number of crayons left.

3. Turn the words into operations.

“ $3$ boxes with $8$ in each” means multiply: $3 \times 8$
“ $7$ crayons are used” means subtract $7$

4. Write the equation.

3 \times 8 - 7 = n

This equation says that the number of crayons in all the boxes, minus the crayons used, equals the number left.

5. Solve and check.

3 \times 8 - 7 = n

24 - 7 = n

17 = n

So, $17$ crayons are left. The equation is correct because both sides have the same value: $3 \times 8 - 7$ and $n$ both equal $17$ .

Learn by doing: Write equations from word problems

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Multiplication Word Problems - Setup (Small Integer Values)

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