Unit 1 - Objective 3 - Calculators and Approximate Numbers
The precision of a measurement is indicated by the position
of the last digit relative to the decimal point.
The significant digits are those that are determined by measurement.
Accuracy refers to the number of significant digits.
To round off a number to a certain number of significant digits, examine the digit in the next place to the right. If this digit is less then 5 (0, 1, 2, 3, 4) then accept the digit in the last place to the left of this digit. If the digit is 5 or more (5, 6, 7, 8, 9) then increase the digit in the last place by one.
Round 5.2348 to the nearest hundredth. The digit in the hundredth place is a 3. The next digit to the right is a 4. Since 4 is less than 5, the 4 and all other digits are dropped. So 5.2348 rounded to the nearest hundredth is 5.23.
Round 7,030.6 to two significant digits. The second digit is a 0. The digit to the right is a 3. Since 3 is less than 5, we accept the second significant digit zero. Each digit between the second significant digit and the decimal point is changed to 0. So 7,030.6 rounded to two significant digits is 7,000.
Round 7,030.6 to three significant digits. The third significant digit is a 3. The digit to the right is a 0. Since 0 is less than 5 we accept the third significant digit 3. So 7,030.6 rounded to three significant digits is 7,030.
Round 7,030.6 to four significant digits. The fourth significant digit is a 0. The digit to the right is a 6. Since 6 is greater than 5, we raise the fourth significant digit by 1 to 1. So 7,030.6 rounded to four significant digits is 7,031.
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