6th Grade Math Textbook, Progress

Estimate Products

2-2

A long time ago, the land an ox could plow

in a day was called an “acre.” Today, an acre

is defined as 4840 square yards. Andy says

that an ox could plow 1,766,600 square yards

in a year. Is Andy’s statement reasonable?

Use estimation to find an approximate

answer or to determine if an exact answer

is reasonable.

To estimate a product by rounding:


Round each factor to its greatest place.


Multiply the rounded factors.

Estimate: 365 
 4840

400 
 5000 2,000,000 square yards

2,000,000 is close to 1,766,600. Andy’s statement is reasonable.

Study these examples.

Estimate: 47 
 18

50 
 20  1000

47 
 18 
 1000

Estimate: 3.42 
 53

3 
 50  150

3.42 
 53 
 150

Estimate: 10.25 
0.87

10 
 0.9  9

10.25 
0.87 
 9

Both factors are rounded

up. The actual product

is less than1000.

Both factors are rounded

down. The actual product

is greater than150.

One factor is rounded

down and the other is

rounded up. The actual

product is close to10.

Estimate each product by rounding. Tell whether the actual product

is greater than, is less than, or is close tothe estimated product.

1. 
   
   
   
   2. 
      
      
      
      3. 
         
         
         
         4. 9.42
            
            74
         
         
         
         
      
      
      
      
   
   
   
   

4.45


 62

491


 52

95


 67

8206-2_068-069 10/7/07 10:50 AM Page 68