Mathematics Magazine for Grades 1-12  

Grade 3

Theory: 

Relationship between Subtraction and Addition

There is an inverse relationship between addition and subtraction.

Example: Since 3 + 7 = 10 then the following are also true:

10 - 3 = 7

10 - 7 = 3

Similar relationships exist for subtraction.
Example: Since 10 - 3 = 7 then the following are also true:

3 + 7 = 10

7 + 3 = 10

An equation is balanced or the same on either side of the equals (=) sign. If exactly the same thing is done to both sides of the equation, it will still be balanced or equal.

In the example above we start with the equation 3 + 7 = 10:

Subtract the same number from both sides 3 + 7 - 3 = 10 - 3

On the left side the 3 and -3 produce 0 which leaves 7 = 10 - 3

Turning the equation around to be in more normal form 10 - 3 = 7

Solutions from the Previous Issue:

Calculate:

1.        17 4 : 2 = 19

2.        1  11 : 11 = 2

3.        19  6 : 19 = 6

4.        3  1 : 3 = 1

5.        14  10 : 5 = 28

6.        12  20 : 6 = 40

Proposed Exercises:

Calculate:

1.        (16 – 8) x (27 : 3) =

2.        (51 – 9) : (12 – 5) =

3.        (54 : 9) x (72 : 9)=

4.        (63 : 9) x (86 – 78) =