Chapter 2: Problem 17
Subtract. $$15-18$$
Short Answer
Expert verified
The result of 15 - 18 is -3.
Step by step solution
01
Identify the Problem Type
We are given the subtraction problem \(15 - 18\). The problem involves subtracting a larger number from a smaller number, which will result in a negative number.
02
Rewrite the Subtraction
Change the subtraction operation into a negative addition: \(15 - 18\) can be rewritten as \(15 + (-18)\). This shows that we're adding a negative number to a positive number.
03
Perform the Addition
Now add \(15\) and \(-18\) together. The result will be negative because \(-18\) has a larger absolute value than \(15\). Calculate: \(15 + (-18) = -3\).
04
Check Your Work
Verify the solution by considering the number line. Starting at 15, moving left 18 places brings you to -3. Thus, the solution is correct.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Negative Numbers
Negative numbers are numbers less than zero. They are commonly represented with a minus sign, such as
-1, -2, -3, and so on. When you subtract a larger number from a smaller one, you get a negative result.
In the example given, subtracting 18 from 15 leads us to a negative number. If you're not used to working with negative numbers, keep these key points in mind:
In the example given, subtracting 18 from 15 leads us to a negative number. If you're not used to working with negative numbers, keep these key points in mind:
- A negative number is always less than zero.
- Negative numbers are the mirror of positive numbers on the number line.
- Think of them as debts or temperatures below freezing.
Number Line
A number line is a visual representation of numbers. It helps in understanding both positive and negative numbers in relation to each other.
A number line has zeros in the center, positive numbers to the right, and negative numbers to the left. It's a powerful tool:
A number line has zeros in the center, positive numbers to the right, and negative numbers to the left. It's a powerful tool:
- For visualizing subtraction and addition.
- To see how negative and positive numbers are arranged.
- To easily track changes in values step by step.
Absolute Value
Absolute value measures the distance of a number from zero on the number line, ignoring direction. It is always a positive number or zero.
The absolute value is crucial in subtraction involving negative numbers:
The absolute value is crucial in subtraction involving negative numbers:
- It helps determine which number has a greater influence when added or subtracted.
- Helps in understanding the size of numbers independent of their sign.
- Is denoted by vertical bars, for example, \(|-18| = 18\).