Ask Dr. Math
Middle School Archive
Dr. Math Home ||
Middle School ||
High School ||
Dr. Math FAQ
See also the
Dr. Math FAQ:
negative x negative
3D and higher
Browse Middle School Negative Numbers
Stars indicate particularly interesting answers or
good places to begin browsing.
Selected answers to common questions:
Inequalities and negative numbers.
Positive/negative integer rules.
- Raising Both Sides of an Inequality to a Power [06/19/2006]
You have to flip the sign in an inequality if you multiply both sides
by a negative number. Is there any rule that says when you have to
flip the sign if you raise both sides to a power?
- Reversing the Inequality [09/21/1998]
Why does the inequality sign reverse when you multiply by a negative
- Reversing the Inequality Symbol [03/09/1999]
Why do we reverse the inequality symbol when dividing/multiplying by a
- Solving x-(-16) = 0 [02/17/1998]
How do you solve: x- -16 = -16?
- Solving -X = 3 [10/26/1998]
How do you solve -X = 3? How can a negative equal a positive?
- Spaces and the Number Line [02/26/2003]
If you say, 'How many degrees are there between -2 and 4?' would you
count the 0 degrees and answer 7 degrees or would you not count the
nought and answer 6 degrees?
- Square Root of 64 [6/20/1996]
I would like to know the square root of 64.
- Square Root of a Negative Number Squared [01/23/1997]
Is Sqrt(-6)^2 equal to 6 or -6?
- Subtracting and Borrowing in a Column [09/05/2002]
A student borrowed in a column as follows: 6.9 - 7.92, to get -2.98.
Why won't borrowing work with this number?
- Subtracting as Adding a Negative [01/14/2002]
My teacher says to think of the question as a negative number, not a
minus number, but I don't know how he's doing that.
- Subtracting Negative Integers [09/12/2001]
I have questions like: -3 - -13. My teacher said to do it in a money
- Subtracting Negative Numbers [05/11/1998]
Can you explain how to subtract a negative number from a positive number
and a positive number from a negative number?
- "Subtraction" and "Negative"--Same Sign, Different Concepts? [12/14/2005]
Why do we use "-" to mean both "subtraction" and "negative", when those are two different concepts?
- Talking About Zero, Absolute Zero and Negative Numbers [11/12/2003]
Are there any useful strategies other than temperature to introduce
negative numbers, and also to teach about zero, its properties, and
how they differ from those of absolute zero?
- Understanding Negative Numbers [5/18/1996]
I don't understand negatives - can you help me?
- Using Cancellation to Add Positives and Negatives [10/27/2003]
How can I memorize the rules for adding positives and negatives?
- What If There Was No Zero? [10/21/2003]
Why did it take so long to discover zero? Why did early civilizations
not need zero? How would math as we know it be different if there was
- What is an Integer? [10/03/2002]
Why isn't -1/2 considered an integer?
- What Sign Do You Use? [10/21/2001]
If two negatives equal a positive, then how do you do it, and what sign
do you take?
- When Do You Flip an Inequality Sign? [12/19/2005]
What does it mean to change the sense of an inequality? When do you
have to do that?
- Why a Negative x Negative = Positive [11/4/1996]
A teacher in a course I took last fall challenged us to come up with a
way to demonstrate or prove how it is that a negative times a negative
equals a positive (how to explain this). The only thing I could come up
with is that it is positive because one is negating a negative.
- Why Aren't There Negative Prime Numbers? [12/10/1999]
Why can't negative numbers be prime numbers?
- Why Does a Negative Times a Negative Equal a Positive? [03/01/1998]
Using the distributive law to reason why a negative times a negative
equals a positive.
- Why Does a Negative Times a Negative Make a Positive? [11/25/2003]
Why is a negative times a negative a positive? When you answered this
question to other people, the way you explained it was over my head.
Can you help me understand this?
- Why Do Two Negatives Equal a Positive? [6/6/1996]
I don't understand why two (-) = the +.
- Why Do We Learn about Negative Numbers? [10/14/2004]
Why do we have to learn about negative numbers? The only context
where I can see it being useful is in determining temperature.
- Why Flip the Inequality Sign? [10/26/2001]
Please tell me why you flip the inequality sign when dividing by a
Search the Dr. Math Library:
© 1994- The Math Forum at NCTM. All rights reserved.
Home || The Math Library || Quick Reference || Search || Help