Integers – Chapter 1/Extra Questions for Practice.

CBSE CLASS 7 MATHEMATICS
Integers – Chapter 1.

Extra Questions for Practice
Answer the following (2 marks):

1. Verify a – (-b) = a + b for the following values of a and b.
i) a = 25, b = 15
ii) a = 75, b= 20
2. Write a pair of integers whose sum gives
i) a negative integer
ii) Zero
3. Write a pair of integers whose difference gives
i) a negative integer
ii) zero
4. In a class test, Manu scored -30, 20, 15 and Sanu scored 20, -15, 25 in three subjects. Who scored more? Can we say that we can add integers in any order?
5. Fill in the blanks to make the following statements true:
i) (-5) + (-7) = ———– + (-5)
ii) 23 + ———- = 0
iii) (3 + (-7)) + (——) = 3 + ((-7) + 5)
6. What will be the sign of the product if we multiply together
i) 8 negative integers and 3 positive integers?
ii) 5 negative integers and 4 positive integers?
7. Find the product:
i) (-1) x (-2) x (-5) x (-6)
ii) (-876) x (-1)
8. Replace the blank with an integer to make it a true statement.
i) (-4) x ——– = 28
ii) 5 x ———- = – 45
9. The product (-9) x (-5) x (-6) x (-3) is positive whereas the product
(-9) x (-5) x 6 x (-3) is negative. Why?
10. Find-

i) (-36) divided by (-4)
ii) (-100) divided by (20)

ANSWERS:

1. i) a = 25, b= 15
LHS = a – (-b) = 25 – (-15) = 25 + 15 = 40.
RHS = a + b = 25 + 15 = 40.
Therefore, LHS = RHS. So verified.
ii) a = 75, b = 20
LHS= a- (-b) = 75 – (-20) = 75 + 20 = 95
RHS = a + b = 75 + 20 = 95.
Therefore, LHS = RHS. So verified.

2. i) (-11) + 6 = -5
ii) (-6) + (+6) = 0

3. i) (-20) –(-4) = (-20) + 4 = -16
ii) 6 – 6 =0

4. Manu’s score = (-30) +20+15 = 5
Sanu’s score = 20 + (-15) +25 = 30
Sanu scored more.
We can add integers in any order. That is known as Commutative property.
Integers are commutative under addition.

5. i) (-5) + (-7) = (-7) + (-5)
ii) 23 + (-23) = 0
iii) [3 + (-7)] +5 = 3 + [(-7) +5]

6. i) If the number of negative integers are even, then the product will be positive. In the given question 8 negative integers are there; since 8 is an even number their product will be positive.
ii) If the numbers of negative integers are odd, then their product will be negative. In the given question 5 negative integers are there, since 5 is an odd number their product will be negative.

7. i) 60
Here number of negative integers are 4; since 4 is an even number their product will be positive. So multiply the numbers and put positive sign.
ii) 876
Here number of negative integers are 2; since 2 is an even number their product will be positive. So multiply the numbers and put positive sign.

8. i) (-4) x (-7) = 28
ii) 5 x (-9) = -45

9. In (-9) x (-5) x (-6) x (-3), the number of negative integers are 4, since it is even their product will be positive whereas in (-9) x (-5) x 6 x (-3), the number of negative integers are 3, since 3 is odd, their product will be negative.

10. i) 9
ii) -5