SLO Know how to multiply and divide negative numbers -6 x –4 = http://www.khanacademy.org/math/arith metic/absolutevalue/mult_div_negatives/v/multiplyingpositive-and-negative-numbers (Khan: multiply negative numbers video) 1 of 42 Multiplying integers 5 x -3 this can be thought of as 5 lots of -3 –3 + –3 + –3 + –3 + –3 = –15 –3 –15 –3 –12 –3 –9 –3 –6 –3 –3 0 5 × –3 = –15 A positive number × a negative number = a negative number 2 of 42 Multiplying negative numbers –7 × 3 = 3 × –7 = –21 –7 –21 –7 –7 –14 –7 0 A negative number × a positive number = a negative number 3 of 42 Multiplying negative numbers –4 × –6 = 24 0 – –6 – –6 – –6 6 12 – –6 18 24 A negative number × a negative number = a positive number 4 of 42 Rules for multiplying and dividing When multiplying negative numbers remember: + × + = + + × – = – – × + = – – × – = + When we are dividing negative numbers similar rules apply: 5 of 42 + ÷ + = + + ÷ – = – – ÷ + = – – ÷ – = + Multiplying/Dividing Integers Copy into your notes 6 of 42 1st Number 2nd Number Answer + – – + + – + – + + – – Copy into note book A way to Remember! To remember whether your answer will be positive or negative when multiplying or dividing, use: Mr. Multiplivision 7 of 42 Copy into your notes E.g. 1 5x -3 Cover the two signs you are using The one that is left is the sign of the answer? = 8 of 42 -15 E.g. 2 -48 -4 Cover the two signs you are using = +12 The sign that is left is the sign of the answer? 9 of 42 Your Turn (1) – 2 × 8 = 10 of 42 -16 (7) 5 × - 7 = -35 (2) – 4 × - 7 = 28 (8) – 7 × - 8 = 56 (3) 5 × - 6 = -30 (9) – 20 × 10 = -200 (4) – 4 × - 3 = 12 (10) 2 2 × -3 = -66 (5) – 7 × 10 = -70 (11) – 20 × -10 = 200 (6) 1 2 × - 2 = -24 (12) 12 × 9 = 108 Your Turn: Complete the following: –3 × 8 = –24 –36 ÷ 42 ÷ –7 = –6 540 ÷ –90 = –6 –12 × –8 = 96 –7 × –25 = 175 47 × –4 × –5 × –8 = –160 3 = 141 –72 ÷ –6 = 11 of 42 12 9 = –4 3 × –8 ÷ –16 = 1.5 Mixed division square 12 of 42 Mixed multiplication square 13 of 42 Mixed division square 14 of 42 SLO Learn how to multiply several negative numbers together 15 of 42 Copy into note book Multiplying Several Integer Factors a. (-1) x (+1) x (-1) = +1 b. (+1) x (+1) x (-1) = -1 If there is an even number of negative signs, the product is positive c. (-1) x (-1) x (+1) = +1 d. (-1) x (-1) x (-1) = -1 16 of 42 If there is an odd number of negative signs, the product is negative Your Turn 1) (-1) x (+1) x (-1) = +1 2) (+1) x (+1) x (-1) = -1 3) (-1) x (-1) x (+1) = +1 4) (-1) x (-1) x (-1) = -1 5) (-1) x (-1) x (+1) x (-1) x (+1) = -1 6) (-1) x (+1) x (+1) x (-1) x (+1) = +1 17 of 42 Your Turn: Multiplying Several Integer Factors a. (-1) x (+1) x (-1) x (+1) = 1 b. (+1) x (+1) x (-1) x(-1) = 1 c. (-1) x (+1) x (-1) x (-1) x (+1) = -1 d. (-1) x (-1) x (-1) x (-1) x (+1) x (-1) = -1 e. (1) x (+1) x (-1) x (-1) x (+1) x (-1) = -1 f. (-1) x (-1) x (-1) x (-1) x (-1) x (-1) = 1 g. (-2) x (-3) x (-2) x (+1) = -12 h. (-1) x (-3) x (-2) x (-2) x (-3) = -36 18 of 42 Your Turn 1) (-2) x (+2) x (-1) x (-3)= -12 2) (+1) x (+4) x (-5) = -20 3) (-17) x (-2) x (+2) = 68 4) (-2) x (-3) x (-6) x (4) = -144 5) (-2) x (-3) x (-3) = -18 19 of 42 Integer cards – multiplication and division 20 of 42 Number spiral –10 –8 –4 2 –11 3 –15 0 –3 21 of 42 –16 6 –2 SLO BEDMAS (order of operations) and negative numbers 22 of 42 Copy into note book Order of Operations With Integers BEDMAS is always used with negative numbers E.g. 3 x (–7) + 4 x (-5) = -21 + -20 = -41 15 + (+5)2 x 2 = 15 + 25x2 = 15 + 50 = 65 (-18) – (-3)2 – 9 x 2 = -18 – 9 – 18 = -45 23 of 42

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