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### Exercise 1.3

#### Question 1

**Fill in the blanks:**

**(i) For any two positive integers a and b, a × (—b) = (—a) × b = ___**

**(ii) For any two positive integers a and b , (-a) × (-b) = ___**

(iii) Product of three negative integers is a ___ integer

(iv) Product of four negative integers is a __ integer

(v) If we multiply 4 positive integers and 3 negative integers , the sign of the product is ___

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#### Question 2

**(i) a × b is an integer , foe all integers a and b **

**(ii) For any two integers a and b , a × b ≠ b × a**

**(iii) For any three integers a , b and c , (a×b)×c = a×(b×c)**

**(iv) For any three integers a , b and c , a×(b+c) = a×b + a×c**

**(v) For any integer a, a×1 = a ; 1 is the multiplicative identity for integers .**

**(vi) For any integer a , a×0=0×a = 0 **

#### Question 3

**Find each of the following products:**

**(i) -5×16**

**(ii) 24×(-3)**

**(iii) 135×0**

**(iv) (-3)×(-3)×(-3)**

**(v) (-5)×(-19)×0**

**(vi) (-4)×(-7)×(-5)×10**

#### Question 4

**Take a =5 , b = -3 and c = 4 , verify that**

**(i) -5×16**

**(ii) 24×(-3)**

**(iii) 135×0**

**(iv) a×(b+c) = a×b + a×c**

**(v) a×(b-c) = a×b – a×c**

#### Question 5

**(i) Find the integer which when multiplied by —1 gives 99**

**(ii) Find the product using suitable property: **

**165 × (-67) + (-165) × 33**

**(iii) Find the product using suitable property: **

**35 + (-35)×(-99)**

#### Question 6

**Every floor of a 20 storey building is 4 m high . A lift moves 2 m per second. How long will it take to move from 4th floor to 14th floor?**

Sol :

#### Question 7

**The temperature of a city was 28°C on Tuesday. The temperature rose by 15°C on everyday upto Friday and fell by 2.5° C on Saturday . What was the temperature of the city on Saturday?**

Sol :