2.5 Properties of Mental Computation

ASSOCIATIVE OF ADDITION DISTRIBUTION COMMUNATIVE OF ADDITION ASSOCIATIVE OF MULTIPLICATION REFLEXIVE

 Ex. 2 At the beginning of this lesson, Skylar used mental computation to calculate the number of tubes stored in 3 sheds { }. Show how the Commutative and Associative Properties are used to regroup the numbers to make the sum easier to compute mentally.  ( ) + 56  ( ) + 56 COMMUNATIVE OF ADDITION  27 + ( ) ASSOCIATIVE OF ADDITION   127

 8 (3.50) = 8 (3) + 8 (.50)   28

 You can find the opposite of a number by multiplying the number by -1.

 A. a + b -1 (a + b) -1(a) + -1(b) -a - b  b. x – 8 -1(x – 8) -1(x) – 1(-8) -1x + 8

 c. –x (-x + 8) -1(-x) -1(8) x -8  d. a – b -1(a – b) -1(a) – 1(-b) -1a + b