Algebra I All-in-One For Dummies. Mary Jane Sterling

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pleasant — colder, lower, smaller.

      Using the number line

      When comparing negative numbers, the number closer to 0 is the bigger or greater number. You may think that recognizing that 16 is bigger than 10 is an easy concept. But what about –1.6 and –1.04? Which of these numbers is bigger?

The easiest way to compare numbers and to tell which is bigger or has a greater value is to find each number’s position on the number line. The number line goes from negatives on the left to positives on the right (see Figure 2-1). Whichever number is farther to the right has the greater value, meaning it’s bigger.

Schematic illustration of a number line ranges from -40 to 40.

      FIGURE 2-1: A number line.

      

Q. Using the number line in Figure 2-1, determine which is larger, –16 or –10.

      A. The number –10 is to the right of –16, so it’s the bigger of the two numbers.

      Q. Which is larger, –1.6 or –1.04?

      A. The number –1.04 is to the right of –1.6, so it’s larger. A nice way to compare decimals is to write them with the same number of decimal places. So rewrite –1.6 as –1.60; it’s easier to compare to –1.04 in this format.

Schematic illustration of another number line ranges from -10 to 10.

      FIGURE 2-2: Another number line.

      1yourturn Which number is larger, 4.6 or math?

      2 Which number is larger, math or 0?

      4 Put the numbers in order from smallest to largest: 4, 0, math, math.

      5 Put the numbers in order from smallest to largest: math.

      Comparing positives and negatives with symbols

Comparison What It Means
math 6 is greater than 2; 6 is farther from 0 than 2 is.
math 10 is greater than 0; 10 is positive and is bigger than 0.
math –5 is greater than –8; –5 is closer to 0 than –8 is.
math –300 is greater than –400; –300 is closer to 0 than –400 is.
math 0 is greater than –6; –6 is negative and is smaller than 0.
math 7 is greater than –80; –80 is negative and is smaller than 0.

      

Positive numbers are always bigger than negative numbers.

      Two other signs related to the greater-than and less-than signs are the greater-than-or-equal-to sign (≥) and the less-than-or-equal-to sign (≤).

Schematic illustration of positive and negative numbers on a number line.

      FIGURE 2-3: Positive and negative numbers on a number line.

      

Q. Write the description using math notation: math is greater than math.

      A. math. The point of the arrow is always in the direction of the smaller of the two numbers.

      Q. Write the description using math notation: math is less than or equal to 0.

      A. math.

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