Multiply integers

Use groups and patterns to understand the multiplication sign rules.

Understand it

Make the idea make sense.

01

Positive groups of a negative value

3 × (−4) means three groups of −4. Combining them gives −4 + (−4) + (−4) = −12. A positive factor and a negative factor produce a negative product.

02

Extend a pattern through zero

Look at (−4) × 2 = −8, (−4) × 1 = −4, and (−4) × 0 = 0. As the second factor decreases by 1, the product increases by 4. Continuing gives (−4) × (−1) = 4 and (−4) × (−2) = 8.

03

Calculate the magnitude, then the sign

Multiply the absolute values. If the non-zero factors have the same sign, the product is positive. If they have different signs, the product is negative. Multiplication is commutative: changing the order of the factors does not change the product.

04

Treat zero as its own case

Any integer multiplied by zero gives zero. Zero is neither positive nor negative, so do not label a zero product as positive or negative.

Words worth knowing
Factor
A number being multiplied.
Product
The result of multiplication.
Magnitude
The size of a value, represented here by its absolute value.
Follow the pattern

What happens beyond zero?

Keep −4 as one factor. Change the other factor by one, then notice how the product changes.

−4 × 2 = −8
Multiples of −4 as the second factor decreases
Second factorExpressionProduct
3(−4) × (3)-12
2(−4) × (2)-8
1(−4) × (1)-4
0(−4) × (0)0
-1(−4) × (-1)4
-2(−4) × (-2)8
-3(−4) × (-3)12

Khan Academy

Pause before the next calculation. Predict the sign and explain the model, then compare the reasoning.

See the thinking

One step at a time.

Predict each next step, then reveal the explanation.

Example 1

(−6) × 4

  1. Multiply the absolute values: 6 × 4 = 24.
  2. The non-zero factors have different signs, so the product is negative.
  3. (−6) × 4 = −24.
Example 2

(−7) × (−3)

  1. Multiply the absolute values: 7 × 3 = 21.
  2. The non-zero factors have the same sign, so the product is positive.
  3. (−7) × (−3) = 21.
Example 3

5 × (−2) × (−3)

  1. Work from left to right: 5 × (−2) = −10.
  2. Then (−10) × (−3) = 30.
  3. The product is 30. Two negative factors give a positive product when the other factors are positive.
Try together

A little support. Your thinking.

Work through (−6) × (−4).

Your turn

Practice with purpose.

New questions, useful feedback and hints that build on your thinking.

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Connections

In the real world

A team loses 4 points for each of 5 penalties. Its total signed change is 5 × (−4) = −20 points.

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