Class 7 Maths Chapter 1 Exercise 1.3 Pdf Notes NCERT Solutions
Class 7 Maths Chapter 1 Integers Exercise 1.1 pdf notes:-
Exercise 1.3 Class 7 maths Chapter 1 Pdf Notes:-
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Ncert Solution for Class 6 Maths Chapter 1 Integers Exercise 1.1 Tips:-
Introduction:-
Multiplication of a Positive and a Negative Integer
We know that multiplication of whole numbers is repeated addition. For example,
5 + 5 + 5 = 3 × 5 = 15
Can you represent addition of integers in the same way?
We thus find that while multiplying a positive integer and a negative integer, we
multiply them as whole numbers and put a minus sign (–) before the product. We
thus get a negative integer
- Find: (a) 15 × (–16) (b) 21 × (–32)
(c) (– 42) × 12 (d) –55 × 15 - Check if (a) 25 × (–21) = (–25) × 21 (b) (–23) × 20 = 23 × (–20)
Write five more such examples. - In general, for any two positive integers a and b we can say
a × (– b) = (– a) × b = – (a × b)
Multiplication of two Negative Integers
Can you find the product (–3) × (–2)?
Observe the following:
–3 × 4 = – 12
–3 × 3 = –9 = –12 – (–3)
–3 × 2 = – 6 = –9 – (–3)
–3 × 1 = –3 = – 6 – (–3)
–3 × 0 = 0 = –3 – (–3)
–3 × –1 = 0 – (–3) = 0 + 3 = 3
–3 × –2 = 3 – (–3) = 3 + 3 = 6
Do you see any pattern? Observe how the products change
So observing these products we can say that the product of two negative integers is
a positive integer. We multiply the two negative integers as whole numbers and put
the positive sign before the product.
Thus, we have (–10) × (–12) = + 120 = 120
Similarly (–15) × (– 6) = + 90 = 90
In general, for any two positive integers a and b,
(– a) × (– b) = a × b
Find: (–31) × (–100), (–25) × (–72), (–83) × (–28)
Game 1
(i) Take a board marked from –104 to 104 as shown in the figure.
(ii) Take a bag containing two blue and two red dice. Number of dots on the blue dice
indicate positive integers and number of dots on the red dice indicate negative integers.
(iii) Every player will place his/her counter at zero.
(iv) Each player will take out two dice at a time from the bag and throw them
(v) After every throw, the player has to multiply the numbers marked on the dice.
(vi) If the product is a positive integer then the player will move his counter towards
104; if the product is a negative integer then the player will move his counter
towards –104.
(vii) The player who reaches either -104 or 104 first is the winner
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