Lesson 2: Estimate Products

Property

To estimate a product $a \times b$, replace the factors with nearby compatible numbers, $c$ and $d$, such that $c \approx a$ and $d \approx b$. The estimate is the product $c \times d$.

Examples

Property

To estimate the product of two numbers, round one or both factors to a nearby place value (like the nearest ten or hundred) to make the multiplication easier to perform mentally. The symbol $\approx$ means "approximately equal to".

Examples

• To estimate $48 \times 7$, round $48$ to the nearest ten, which is $50$. Then, calculate $50 \times 7 = 350$. So, $48 \times 7 \approx 350$.

• To estimate $615 \times 4$, round $615$ to the nearest hundred, which is $600$. Then, calculate $600 \times 4 = 2400$. So, $615 \times 4 \approx 2400$.