This question has two parts. First, answer Part A. Then, answer Part B.
Part A
Select the correct choices to complete the sentence.
Erica wants to find the product of  2.145×0.72
 .

 

First, estimate the product of  2.145×0.72
 .

 

2.145 can be rounded 1 of 5.
Select Choice
 to 2 of 5.
Select Choice
.

 

0.72 can be rounded 3 of 5.
Select Choice
 to 4 of 5.
Select Choice
.

 

A reasonable estimate is 5 of 5.
Select Choice
.

Part B
Find  2.145×0.72
 . Compare your estimate with your answer. What can you conclude?

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### **Part A**  
Erica wants to find the product of \(2.145 \times 0.72\). Let’s proceed step-by-step to estimate the product by rounding the numbers.

1. **Step 1: Round 2.145**  
   - \(2.145\) can be reasonably rounded **to 2** (since it’s close to 2).  
   
2. **Step 2: Round 0.72**  
   - \(0.72\) can be reasonably rounded **to 0.7** (since it’s slightly above 0.7).  

3. **Step 3: Estimate the product**  
   - Now, multiply the rounded numbers:  
     \[
     2 \times 0.7 = 1.4
     \]

   **A reasonable estimate is 1.4.**

---

### **Part B**  
Now, let’s calculate the exact product of \(2.145 \times 0.72\).

\[
2.145 \times 0.72 = 1.5432
\]

---

### **Comparison and Conclusion**  
- **Estimate vs Exact Product:**  
  The estimate was \(1.4\), and the exact product is \(1.5432\).  
- **Conclusion:**  
  The estimate \(1.4\) is close to the exact answer \(1.5432\), showing that rounding gives a reasonable approximation, though it slightly underestimates the exact value.

---

Would you like further clarification or detailed steps on any part?  

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**Related Questions:**  
1. How does rounding affect the accuracy of an estimate?  
2. What is the best way to decide how many decimal places to round to?  
3. How does multiplication by decimals impact the product size?  
4. What is the difference between rounding and truncating?  
5. How do you determine if an estimate is "reasonable"?  

**Tip:**  
When working with decimals, it's helpful to estimate first to verify if the final answer makes sense.

This question has two parts. First, answer Part A. Then, answer Part B.

Part A
Select the correct choices to complete the sentence.
Erica wants to find the product of  2.145×0.72.

First, estimate the product of  2.145×0.72.

2.145 can be rounded to 2.
0.72 can be rounded to 0.7.

A reasonable estimate is 1.4.

Part B
Find  2.145×0.72. Compare your estimate with your answer. What can you conclude?

Learn how to estimate and calculate the exact product of 2.145 × 0.72. This example teaches estimation through rounding and compares the estimate with the actual product, helping students understand the importance of estimation in calculations. Suitable for Grades 5-7.

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