Working With Signed Numbers
By Stephen Bucaro
Working with signed numbers is easy, it requires only a few easy rules. But if you don't work with
signed numbers every day, you could easily forget the rules.
Rules for Adding Signed Numbers
• If one of the numbers is zero - Any number plus zero is that number.
• If both numbers are positive - Add the numbers, the sum is positive.
• If both numbers are negative - Add the numbbers, the sum is negative.
• If one number is positive and One is negative - Subtract the smaller number from the larger number.
The sign of the answer, called the sum, is the sign of the largest absolute value number.
Absolute value means the number without the sign.)
If a number is positive, we usually leave out the sign, and +0 and -0 are both the same
thing, just 0 (zero).
Examples
| 46 + 0 = 46 | Any number plus zero is that number |
| 27 + 46 = 73 | Both numbers are positive - Add the numbers, the sum is positive. |
| -27 + (-46) = -73 | Both numbers are negative - Add the numbbers, the sum is negative. |
| 27 + (-46) = -19 | One number is positive and one is negative - Subtract the smaller number from the larger number. Here -46 is the largest number. |
| -27 + 46 = 19 | One number is positive and one is negative. Here 46 (+46) is the largest number. |
Rule for Subtracting Signed Numbers
• Change the sign of the number being subtracted, then add using the rules for adding signed numbers.
Examples
| 46 - 0 = 46 - (+0) = 46 | Whether you add zero, to or subtract zero from a number, the answer is always that number. |
| 0 - 46 = 0 + (-46) = -46 | One number is positive and one is negative - Subtract the smaller number from the larger number. Here -46 is the largest number. |
| 27 - 46 = 27 + (-46) = -19 | One number is positive and one is negative. The sign of the sum is the sign of the largest (absolute value) number. Here -46 is the largest number. |
| 46 - 27 = 46 + (-27) = 19 | One number is positive and one is negative. The sign of the sum is the sign of the largest (absolute value) number. Here 46 (+46) is the largest number. |
The subtrahend is the second number in a subtraction, the number to be subtracted.
The first number in a subtraction, the minuend is the number from which the subtrahend
is to be subtracted.
Multiplying Signed Numbers
• If one of the numbers is zero - The answer is always zero.
• If both numbers have the same sign - Multiply the numbers, the answer is always positive.
• If the Numbers have different signs - Multiply the numbers, the answer is always negative.
Examples
| 12(0) = 0 | If one of the numbers is zero - The answer is always zero. |
| 0(-9) = 0 | If one of the numbers is zero - The answer is always zero. |
| 8(4) = 32 | If both numbers have the same sign - Multiply the numbers, the answer is always positive. |
| (-8)(-4) = 32 | If both numbers have the same sign - Multiply the numbers, the answer is always positive. |
| 12(-4) = -48 | If the Numbers have different signs - Multiply the numbers, the answer is always negative. |
| (-3)10 = -30 | If the Numbers have different signs - Multiply the numbers, the answer is always negative. |
The multiplicand is a number that is to be multiplied by another number (the multiplier).
The multiplier is the number of times the multiplicand gets multiplied. It doesn't matter which comes
first, the result, the product is the same either way.
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