Answer :
- Round each number to the nearest whole number.
- Multiply the rounded numbers in each expression to estimate the product.
- Compare the estimated products to 45.
- The expression with the closest estimated product to 45 is $8.7 \times 5.28$, which rounds to $9 \times 5 = \boxed{45}$.
### Explanation
1. Understanding the Problem
We are given four multiplication expressions: $44.7
\times 2.1$, $75
\times 84$, $8.7
\times 5.28$, and $38.1
\times 7.3$. We want to find the expression whose estimated product is $45$.
2. Estimation Strategy
To estimate the product of each expression, we will round each number to the nearest whole number and then multiply the rounded numbers.
3. Calculating Estimated Products
1. $44.7
\times 2.1$ rounds to $45
\times 2 = 90$.
2. $75
\times 84$ remains as $75
\times 84 = 6300$.
3. $8.7
\times 5.28$ rounds to $9
\times 5 = 45$.
4. $38.1
\times 7.3$ rounds to $38
\times 7 = 266$.
4. Identifying the Correct Expression
Comparing the estimated products to $45$, we see that $8.7
\times 5.28$ has an estimated product of $45$.
5. Final Answer
Therefore, the expression with an estimated product of $45$ is $8.7
\times 5.28$.
### Examples
Estimating products is useful in everyday situations, such as when you want to quickly calculate the approximate cost of multiple items at a store. For example, if you are buying 9 items that cost around $5 each, you can estimate the total cost to be $9 \times 5 = $45. This helps you to quickly assess if you have enough money or if the price seems reasonable.
- Multiply the rounded numbers in each expression to estimate the product.
- Compare the estimated products to 45.
- The expression with the closest estimated product to 45 is $8.7 \times 5.28$, which rounds to $9 \times 5 = \boxed{45}$.
### Explanation
1. Understanding the Problem
We are given four multiplication expressions: $44.7
\times 2.1$, $75
\times 84$, $8.7
\times 5.28$, and $38.1
\times 7.3$. We want to find the expression whose estimated product is $45$.
2. Estimation Strategy
To estimate the product of each expression, we will round each number to the nearest whole number and then multiply the rounded numbers.
3. Calculating Estimated Products
1. $44.7
\times 2.1$ rounds to $45
\times 2 = 90$.
2. $75
\times 84$ remains as $75
\times 84 = 6300$.
3. $8.7
\times 5.28$ rounds to $9
\times 5 = 45$.
4. $38.1
\times 7.3$ rounds to $38
\times 7 = 266$.
4. Identifying the Correct Expression
Comparing the estimated products to $45$, we see that $8.7
\times 5.28$ has an estimated product of $45$.
5. Final Answer
Therefore, the expression with an estimated product of $45$ is $8.7
\times 5.28$.
### Examples
Estimating products is useful in everyday situations, such as when you want to quickly calculate the approximate cost of multiple items at a store. For example, if you are buying 9 items that cost around $5 each, you can estimate the total cost to be $9 \times 5 = $45. This helps you to quickly assess if you have enough money or if the price seems reasonable.
