A model with 3 rows of 5 squares and 3 rows of 3 squares.

Question

Use the model to find the missing number in the pair of equivalent expressions.

15 + 9 = ?(5 + 3)

What number is missing from the expression?

Answer 1

To find the missing number in the equivalent expressions \( 15 + 9 = ?(5 + 3) \), we can first simplify the right side of the equation.

First, calculate \( 5 + 3 \): \[ 5 + 3 = 8 \]

Now we replace this in the equation: \[ 15 + 9 = ? \times 8 \]

Next, calculate \( 15 + 9 \): \[ 15 + 9 = 24 \]

So now the equation looks like this: \[ 24 = ? \times 8 \]

To find the value of \( ? \), we can divide both sides of the equation by 8: \[ ? = \frac{24}{8} = 3 \]

Thus, the missing number in the expression is \( 3 \). Therefore, the complete expression is: \[ 15 + 9 = 3(5 + 3) \]