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Word Problems

Browse Elementary Multiplication
Stars indicate particularly interesting answers or good places to begin browsing.

Selected answers to common questions:
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    Learning to multiply.
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Proving That (-1) * (-1) = 1 [01/30/2006]
At the high school level it is difficult to prove that -1 x -1 = 1. Is there a published proof somewhere that is appropriate for kids that age?

Rapid Multiplication ... Diagonally? [02/24/2010]
Doctor Vogler describes the "accumulator" method for finding products of two multi-digit terms, then works through an example.

Rectangular Arrays to Teach Multiplication [11/10/1994]
I teach fourth grade math. Are rectangular arrays the best way to teach multiplication?

Russian Peasant Multiplication [08/19/1997]
I have a project to do on "Russian" or "peasant" multiplication.

Russian Peasant Multiplication [11/01/1997]
What is Russian peasant multiplication?

Square Numbers [07/27/1999]
Can you explain what a square number is?

Squaring Two-Digit Numbers Ending in 5 [09/10/2001]
Take the first digit, multiply it by the next consecutive number, and place it in front of 25. Can you prove this shortcut?

Sum of Products [11/01/1999]
When a word problem refers to the sum of the products, what exactly does it mean?

The Term Power [10/23/2001]
One of my students asked how we came to use the term power to express the number of times we multiply a number by itself.

Times Greater Than, Times As Much As [05/02/1999]
A number is five times greater than x. Will this number be 6x or 5x?

To Multiply or Divide? That Is the Question. [09/02/2003]
In a story problem, how do you know whether to multiply or divide?

Using Doubling to Multiply [02/20/2002]
Can you think of a way to use doubling to multiply 6 x 7?

Using the Distributive Property [08/23/2001]
My math teacher told us to work problems like this: a(b-c)= ab-ac.

Ways to Add and Divide More Easily [11/17/2008]
I have to add 2398 and 5752 and then divide by 37. I can do it, but it takes a long time. Is there any faster way to do those calculations?

What is 65 Times Ten Million? [3/29/1995]
What is 65 times ten million? Also, we've had pluses, multiples, and times. Are there going to be any new things after that?

What is 75% of $5000? [1/2/1995]
What is 75 percent of $5,000?

What is a Multiple? [12/4/1995]
What is the definition of a multiple?

What is multiplication? [11/09/1997]
What does multiplication have to do with addition, geometry, and real life?

Why Cancel? [02/25/2003]
Why do we have to cancel numbers?

Why Casting Out Nines Works [10/13/2008]
Can you explain in simple terms why the Casting Out Nines method works?

Why Does OF Mean Multiply? [12/04/2001]
I wanted to know why the word "of" means multiplication.

Why Is Mental Math Important? [03/25/2004]
How can I convince a 14 year old girl who is in 8th grade the importance of mental math? I think that skills like mentally adding and subtracting 2 digit numbers and being able to estimate multiplying 2 digit large numbers are critical. My daughter's teacher says that such skills aren't needed because of calculators and computers.

Why Multiplying by 10 Just Adds a Zero at the End [10/18/2005]
My 8-year old is having trouble understanding why multiplying by 10 just adds a 0 to the end of the number. Do you have any thoughts on how to explain it to her?

Why Rules? [08/15/2001]
Why do we need to have rules for order of operations?

The Zero Power of Two [12/10/1998]
Why is 2 to the 0 power equal to 1? I don't understand how a number can be multiplied by itself zero times.

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