Page 7 - SM inner class 7.cdr
P. 7
So lu tion : (iii) -8, -7
(i) + 13, + 9 (-8 ) (-7 )
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7
(Like signs rule) = + (8 ´ ) = + 56
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(+ 13 ) (+ 9 ) (Like signs rule)
= + (13 ´ ) = + 117 (iv) + 25, -6
9
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(ii) -11, + 11 (+ 25 ) (-6 )
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6
(-11 ) (+ 11 ) = -(25 ´ ) = -150
= -(11 11 ) = -121 (Unlike signs rule)
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(Unlike signs rule)
E xercise 1.1
1. Fill in the boxes.
)
9
)
3
´
) =
´
(a) (+ 6 ) (- = W (b) (- ´ W =81 (c) (-2 ) (+ 8 W (d) W ´ +( 11 ) =121
(e) W ´ - =( 7 ) 56 (f) -25 W = -75 (g) ( ) ( )- ´ - =W (h) ( ) ( )+ ´ - =W
´
2. Find the sum of the fol low ing.
(a) + 3, + 4 (b) - -6, 2 (c) + 5, -5 (d) - +7, 8
(e) - -9, 4 (f) + 3, -8 (g) -10, -5 (h) +11, -7
(i) - -9, 8 (j) + 6, +12 (k) - +3, 50 (l) - +7, 7
(m) - -4, 9 (n) - -5, 13 (o) +110, -8
3. Sim plify each of the fol low ing.
´
´
´
´
´
´
(a) (-1 ) (-1 ) (-1 ) (-1 ) (b) (+1 ) (-2 ) (+ 3 ) (+4 )
2
3
´
´
´
´
(c) [(+2 ) (+ 9 )] (-4 ) (d) [(-18 ) ( )] ( )
(e) [( ) (25 ´ - 8 )] ( 16 ) (f) [(-100 ) (-15 )] ( )
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´
3
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Division of Integers
Division is a reverse process of multiplication. Rule 1 :In te gers with like signs :
To make it clear consider the following example: When an integer is divided by another integer of same
sign, the result is always positive.
2 ´ 3 = Þ = 2
3 æ ö
4
(i) (+ 4 ) ¸ (+ 2 ) = + ç ÷ = (+ 2 )
2
Try to guess the number to fill the boxes. è ø
Obviously 6 is the required number in both æ 4
- ö
cases. So our problem can be solved by putting (ii) (-4 ) ¸ (-2 ) = + ç ÷ = (+ 2 )
- ø
è 2
6 in the boxes i.e.,
6
2 ´ 3 = 6 Þ = 2 Rule 2 : In te gers with un like signs :
3
When an integer is divided by another integer of
It means 2 ´ 3 = 6 can be written as opposite sign, the result is always negative.
6 4
æ ö
2 = . (i) (+ 4 ) ¸ (-2 ) = - ç ÷ = (-2 )
3 è ø
2
Now we discuss the rules for division. æ 4
- ö
(ii) (-4 ) ¸ (+ 2 ) = - ç ÷ = (-2 )
- ø
è 2
7
Mathematics In Focus - 7
