Multiplying Numbers
Properties and Facts of Multiplication
Multiplication algorithm: Please review multiplication facts and the
multiplication algorithm.
Vocabulary: The product of two numbers a and b is a•b. The “a†and “bâ€
are called factors. The product may be written “ab†(omit the dot
between the letters) if the at least one of the factors is a variable.
| English Words |
Math Symbols |
| The product of 2 and 5
|
2·5 |
| The product of 2 and y
|
2·y |
| The product m and n
|
m·n |
| The product of x and 2
|
x·2 |
| The product of p and q
|
p·q |
Properties of multiplication:
Multiplication property of zero: If a is any number, then
a•0 = 0•a = 0
Multiplication property of one: If a is any number, then
a•1= 1•a = a
Commutative property of multiplication: If a and b are any
numbers, then
a•b = b •a
Associative property of multiplication: If a, b and c are any
numbers, then
a (bc) = (ab)c
Solving equations by inspection:
Example:
Solve by inspection.
5n = 25
n = 5 (guess the solution)
Multiplying by powers of ten:
To multiply by a power of ten, count
the number of zeros on the power of ten and place that many
zeros on the end of the other factor to get the answer.
Example:
100 •27 = 2700
To multiply by a number that ends in zeros:
1. Drop the zeros.
2. Multiply the two remaining numbers.
3. Place the zeros at the end of the product.
Example:
2700 •3 = 8100
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