Addition and Subtraction: Make True Equations

Introduction:

1. Pick the equations that are true: –

a. 6 = 12 – 6

b. 7+ 8 = 8 + 7

c. 10 = 10

d. 7 + 3 = 3 + 7

Answers:

a. 6 = 12 – 6, subtract 6 from 12; the answer is 6.

6 = 6, the equation is true.

b. 7 + 8 = 8 + 7; both side equations are true.

c. 10 = 10; both side equations are true.

d. 7 + 3 = 3 + 7; both side equations are true

2. Make the equation true.

1. 4 + 6   = _____ + 1

Answer:

Solve one side of the equation first 4 + 6 =10.

to get the other side of the equation, subtract 1 from 10

10 = 9 + 1. The answer is 4 + 6 = 9 + 1

This equation is true.

3. Fill in the missing number to make this equation true: –

14 – ___ = 3 + 3

Solve one side of the equation first.

3 + 3 = 6

You can use counters to find the missing answer.

14 – ___ = 6

Take away 8 counters to get 6; the answer is 14 – 8 =6.

14 – 8 = 3 + 3. This equation is true.

Solve The Following: –

1. Observe the box. How many balls do you need to add to make the equation true?

6    +   ___ =   10

To get the missing number, subtract the counters ball, i.e.,     

6 from 10, 

10 – 6   = 4

Answer:

2. Make the equation true: –

15 – ____ =   10 + 2

Answers:

Solve one side of the equation first.

10 + 2 =   12

To get the other side of the equation, subtract 12 from 15.

15 – 12 = 3

So, the missing number is 3.

15 – 3 = 10 + 2

The equation is true

3. Write the missing symbol {+, -, or =} and make the equation true.

17 ___ 9 ___ 4 + 4

Answers: –

To get the answer, observe the equation.                                                                   

Solve one side of the equation [symbol inserted here] 4 + 4 = 8

Other side values are more than the next side; so, to get lesser values, you need to insert subtraction symbol, 17 – 9.

Subtract 17 – 9 = 8; both the side values are the same, so insert an equal sign in the middle of both equations.

The answer is 17-9=4+4.

4. Alex has a 15-meter-long rope. He made it into two pieces. One piece is 8 m long. What is the length of the other piece?

15 – 8 = ____

Answer:

Use counters and subtract the missing number.

Take away 8 counters from 15; the answer is 7.

15-8=7. The length of another piece is 7 meters.

• Peter has 14 red crayons; his brother gave him 6 more crayons. John has 12 red crayons. His father gave him 8 more crayons. Do they have an equal number of crayons?

Answer:

Peter has 14+6 crayons. When we add, you get the answer 20.

John has 12+8 crayons. When we add, you get the answer 20.

14+6=12+8

Both of them have an equal number of crayons.

Concept Summary