Question

III. True or False :
1. (-90) + (-30) = 60
2. (-45) – (-8) = (-8) - (-45)
3. (-15) x 5 = 75
4. x + (-x) = 0
5. Sum of a-b+c and -a+b-c is zero.
Y
11
C​

Answer 1

$\sf\huge {\underline{\underline{{Solution}}}}$

1. (-90) +(-30) = 60

Removing brackets and expanding

=> -90-30

= -120 ≠ 60

Hence, it is false

2. (-45 ) -(-8) = (-8)-(-45)

Opening the brackets and expanding the values

solving LHS

=> -45 +8

= -37

Solving RHS

=> -8+45

= 37

since , -37≠ 37 both values are same but having different signs so, it is false .

3. (-15) x 5 = 75

= -75

Here , -75 ≠ 75

False

4. sum of a-b+c and -a+b -c is zero

=>( a-b+c) +( -a+b-c)

=> a-b+c -a +b-c

=> a-a -b+b+c-c

= 0

Hence, LHS = RHS

Therefore, it is true

Concept:

Plus minus = minus

minus minus = plus ( but sign of minus )

In multiplication

minus * minus = +ve value

plus * minus = -ve value

In Division

-ve value ÷ - ve value = +ve value

Positive ( value ) ÷ negative ( value ) = -ve value

Answer 2

1 false

2 false

3 false

4 true

Hope it will help you a lot