Express c in Inequalities: -9 < c < -1 on Number Line

Compound Inequalities with Number Line Visualization

c c is a negative number greater than -9 and less than -1 .

Write this as an expression using the number line below as an aid.

-10-10-10-9-9-9-8-8-8-7-7-7-6-6-6-5-5-5-2-2-2-3-3-3-4-4-4-1-1-1000

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1

Understand the problem

c c is a negative number greater than -9 and less than -1 .

Write this as an expression using the number line below as an aid.

-10-10-10-9-9-9-8-8-8-7-7-7-6-6-6-5-5-5-2-2-2-3-3-3-4-4-4-1-1-1000

2

Step-by-step solution

First, we'll mark the expression C<0 C < 0 on the number line:

-10-10-10-9-9-9-8-8-8-7-7-7-6-6-6-5-5-5-2-2-2-3-3-3-4-4-4-1-1-1000

Then we'll mark C>9 C > -9 :

-10-10-10-9-9-9-8-8-8-7-7-7-6-6-6-5-5-5-2-2-2-3-3-3-4-4-4-1-1-1000

Finally, we'll mark C<1 C < -1 :

-10-10-10-9-9-9-8-8-8-7-7-7-6-6-6-5-5-5-2-2-2-3-3-3-4-4-4-1-1-1000

Now we can see that the section marked in orange overlaps the expression:

-10-10-10-9-9-9-8-8-8-7-7-7-6-6-6-5-5-5-2-2-2-3-3-3-4-4-4-1-1-1000

The numbers that create the overlapping section are those from -9 to -1 and represent the expression in question:

9<c<1 -9 < c < -1

3

Final Answer

9<c<1 -9 < c < -1

Key Points to Remember

Essential concepts to master this topic
  • Rule: Compound inequalities combine two conditions with AND logic
  • Technique: -9 < c means c > -9, and c < -1 gives -9 < c < -1
  • Check: Pick test value like c = -5: -9 < -5 < -1 is true ✓

Common Mistakes

Avoid these frequent errors
  • Writing separate inequalities instead of compound form
    Don't write c > -9 and c < -1 as separate statements = missed connection! This loses the relationship showing c must satisfy BOTH conditions simultaneously. Always combine into -9 < c < -1 to show the complete range.

Practice Quiz

Test your knowledge with interactive questions

What is the distance between 0 and F?

AAA-5-5-5BBB-4-4-4CCC-3-3-3DDD-2-2-2EEE-1-1-1FFF000GGG111HHH222III333JJJ444

FAQ

Everything you need to know about this question

Why can't I write this as c > -9 and c < -1?

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While technically correct, the compound inequality -9 < c < -1 is much clearer! It shows the complete range in one expression and matches what you see on the number line.

How do I know which direction the inequality signs go?

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Think of it as a chain: -9 is less than c, and c is less than -1. So we write -9 < c < -1, reading from smallest to largest value.

What does the number line show exactly?

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The number line shows all values between -9 and -1 are highlighted. The open circles at -9 and -1 mean these endpoints are NOT included in the solution.

Could c equal -9 or -1?

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No! The problem states c is greater than -9 and less than -1. This means c can be -8.9 or -1.1, but never exactly -9 or -1.

How can I check if my inequality is correct?

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Pick any number between -9 and -1 (like -5 or -3) and verify: Is -9 < -5 < -1? Yes! Try a number outside the range like -10: Is -9 < -10 < -1? No, so -10 is correctly excluded.

What if I wrote -1 > c > -9 instead?

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That's also correct mathematically! However, -9 < c < -1 is preferred because it follows the natural order from smallest to largest, making it easier to read and understand.

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