6th Grade Math Textbook, Fundamentals

(Marvins-Underground-K-12) #1
Lesson 4-6 for exercise sets. &KDSWHU 

3UDFWLFH   $FWLYLWLHV

When you multiply more than two factors, you can use the Commutative and

Associative Properties of Multiplication to change the order and grouping
of factors. These properties can help you use mental math.
Multiply: 4 • 2.07 • (0.25)
4 • (0.25) • 2.07 Use the Commutative Property.
[4 • (0.25)]• 2.07 Use the Associative Property.
 1 • 2.07 Simplify.
2.07

Multiply: 1.3 • (0.07)


  • First estimate by rounding: 1 • (0.1) 0.1

  • Then multiply the original numbers to find the actual product.


So 1.3 • (0.07) 0.091.

Check:0.091 is close to the estimate of 0.1, so the answer is reasonable.

The product of two rational numbers
with likesigns is positive.

Write a placeholder zero to fill the decimal place.

2


Remember:


  • When the number of negative factors is even,
    the product is positive.

  • When the number of negative factors is odd,
    the product is negative.


You can also apply the Distributive

Property when multiplying decimals.
Evaluate a(bc) when a2.5, b0.4, and c0.8.
a(bc) 2.5(0.40.8) Substitute 2.5 for a, 0.4 for b, and 0.8 for c.
[(2.5)(0.4)] [(2.5)(0.8)] Use the Distributive Property of Multiplication over Addition.


  1. 0 0  (2.00)
    1. 0 0  1


Distributive Property of Multiplication over Addition:
a(b c) (ab) (ac)

0.07
1. 3
21
 70
0.091

2 decimal places
1 decimal place

3 decimal places

Find the product.
1.2.6(0.013) 2.(0.5)(0.08) 3.0.45 • 5.02 4.(0.0375)(2) 5.(2.5)(4.1)(2)
6.7.2(0.6 0.4) 7.3.2(0.2 0.5) 8.6.15(0.45) 9.(0.205)(2) 10.(5.01)(3)


  1. Evaluate: (ab)c, when a0.2, b0.6, and c1. 2


12.Discuss and Write Explain how using the properties of multiplication can
help you multiply decimals more easily. Show examples to justify your answer.
Free download pdf