6th Grade Math Textbook, Progress

Update your skills. See page 7.

Subtraction Equations

4-6

John caught a 5.2-lb fish. This was 3.9 lb less than the

fish Sarah caught. How much did Sarah’s fish weigh?

To find how much Sarah’s fish weighed,

write and solve an equation.

Let frepresent the weight of Sarah’s fish.

weight of Sarah’s fish minus 3.9 equals weight of John’s fish

f 
 3.9  5.2 subtraction equation

Add 3.9 to bothsides

to isolate the variable.

Addition Property of Equality

When you add the same number to both sides

of an equation, you get a true statement.

To solve a subtraction equation,

use the Addition Property of Equality.

f 
3.9 5.2

f 
3.9 3.95.23.9

f 9.1

Check: f
3.95.2

9.1
3.9 

?

5.2

5.25.2 True

Sarah’s fish weighed 9.1 lb.

Study these examples.

Solve: 3125
y  1527

When the subtrahend is the unknown,

use a related fact to find its value.

3125 
y 1527

3125 
 1527 y

1598 y

Check: 3125 
y 1527

3125 
 1598 

?

1527

1527  1527 True

Solve: a
(293.1)5.3

a
(293.1)5.3

a
32.15.3

a 
32.132.15.332.1

a37.4

Check: a
(293.1)5.3

37.4
(293.1)5.3

37.4
32.1 

?

5.3

5.35.3 True

Write the

related fact.

Simplify.

Related Subtraction Facts:

a
bcand a
cb

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