32 Chapter 1 Whole Numbers Section 1.4 Rounding and Estimating 40 45 48 50 Round up to 50. On the other hand, 43 is closer to 40 than to 50. Therefore, 43 rounded to the nearest ten is 40. 40 43 45 50 Round down to 40. Note 45 is halfway between 40 and 50. In such a case, our convention will be to round up to the next-larger ten. 40 45 50 Round up to 50. The decision to round up or down to a given place value is determined by the digit to the right of the given place value. The following steps outline the procedure. Rounding Whole Numbers Step 1 Identify the digit one position to the right of the given place value. Step 2 If the digit in step 1 is a 5 or greater, add 1 to the digit in the given place value. Then replace each digit to the right of the given place value by 0. Step 3 If the digit in step 1 is less than 5, replace it and each digit to its right by 0. Note that in this case, the digit in the original given place value does not change. Concept Connections 1. Is 82 closer to 80 or to 90? Round 82 to the nearest ten. 2. Is 65 closer to 60 or to 70? Round the number to the nearest ten. Answers 1. Closer to 80; 80 2. The 65 is the same distance from 60 and 70; round up to 70. 1. Rounding Rounding a whole number is a common practice when we do not require an exact value. For example, Madagascar lost 3956 mi2 of rainforest between 1990 and 2008. We might round this number to the nearest thousand and say that there was approximately 4000 mi2 lost. In mathematics, we use the symbol to read “is approximately equal to.”Therefore, 3956 mi2 4000 mi2. A number line is a helpful tool to understand rounding. For example, 48 is closer to 50 than it is to 40. Therefore, 48 rounded to the nearest ten is 50. Concepts 1. Rounding 2. Estimation 3. Using Estimation in Applications
miller_basic_college_math_3e_ch1_3
To see the actual publication please follow the link above