Math Intervention 3–5 Grade

104 Addition and Subtraction Concepts

What is the Equal Difference Concept?

The equal difference concept is a subtraction strategy based

on the idea that different subtraction expressions can have

the same difference. The focus is on the value between

numbers, for example, 76 – 29 = 77 – 30. By adding one to the

subtrahend and one to the minuend, we create an expression

that is more easily solved. In some situations, it makes sense

to add two to the subtrahend and the minuend, for example,

52 – 28 = 54 – 30. In some situations, we may subtract from

the subtrahend and the minuend to create a new expression

with the same difference. For example, 68 – 41 = 67 – 40 or

96 – 82 = 94 – 80. Understanding how to mentally create

expressions with the same differences helps students learn to

build fl exibility and fl uency with numbers and operations.

CCSS

Operations and Algebraic Thinking

Number and Operations in Base Ten

Formative Assessment

To fi nd out if a student understands the equal difference

concept, ask the student if the following equations are true or

not:

54 – 29 = 55 – 30 87 – 34 = 90 – 31

76 – 48 = 78 – 50 81 – 34 = 80 – 33

Ask the student to explain why these equations are true

or not true (the third equation is NOT true). Notice if the

student solves each side of the equation to verify the answer

or if the student uses the equal difference concept.

Equal Differences

CONCEPT: