MathematicsClass 7Integers
Multiplication of Integers
Mastering the sign rules for multiplying positive and negative integers.
Class 7 · MathematicsCBSE & ICSE SOF IMO
Definition
Multiplication of integers is repeated addition with attention to the signs of the numbers. The product of two integers with the same sign is always positive, while the product of two integers with different signs is always negative. Zero multiplied by any integer always results in zero.
Key formula
(-) × (-) = (+) ; (+) × (-) = (-)
Worked examples
1
Multiplying -4 by +5 results in -20 because the signs are different.
2
Multiplying -6 by -3 results in +18 because both integers are negative.
3
Calculating the product of 7, -2, and -3: (7 × -2) = -14, then (-14 × -3) = +42.
Common mistakes
- • Applying the addition rule of signs to multiplication, resulting in incorrect positive or negative outcomes.
- • Forgetting to count the number of negative factors in a long string of multiplication to determine the final sign.