Multiplication of signed numbers
- To multiply two numbers having like signs, multiply their absolute values and prefix a plus sign (or no sign).
- To multiply two numbers having unlike signs, multiply their absolute values and prefix a minus sign.
Example:
(+5) x (+7) = (+35)
(-3) x (-8) = (+24)
(-4) x (+9) = (-36)
(+6) x (-2) = (-12)
Rules of signs
( + ) x ( + ) = ( + )
( + ) x ( - ) = ( - )
( - ) x ( - ) = ( + ) ( - ) x ( + ) = ( - )
In finding the product of more than two numbers, you must remember that we operate on only two numbers at a time. So we start by finding the product of any two and continue until we have used all the factors.
(+2)x(-3)x(+4)=(-6)x(+4)=-24
An easy way to find the sign of the product is to count the number of minus signs. An even number of minus signs will produce a positive product.
Note: The multiplication sign can be omited: (+3)x(-7) = (+3)(-7) = (-21)
