Subtraction and Addition Relationships

This lesson covers Math 7 Unit 6 Lesson 18, focusing on subtraction in equivalent expressions. The key takeaway is that subtraction can be rewritten as adding the opposite. The lesson includes a number talk activity for mental math with sums and differences, a helpful observation activity on rewriting subtraction expressions, and an exploration of the distributive property to find area and equivalent expressions. An additional activity explores algebraic patterns using calendar dates. The lesson concludes with a summary and homework instructions.

What is the key takeaway about subtraction problems discussed in the lesson?

• Subtraction problems can be solved using multiplication.

• Subtraction problems can be rewritten as adding the opposite.

• Subtraction problems cannot be simplified.

• Subtraction problems are always more complex than addition problems.

In the mental math activity, what is the result of adding -30 and -10?

• 20

• -20

• 40

• -40

Why can't you switch the order of numbers in a subtraction problem like you can with addition?

• Because subtraction is not commutative.

• Because subtraction is associative.

• Because subtraction is distributive.

• Because subtraction is reflexive.

What is the advantage of rewriting a subtraction problem as an addition problem?

• It makes the problem more complex.

• It changes the value of the expression.

• It allows for easier computation and rearrangement.

• It eliminates the need for common denominators.

How can the area of a rectangle be expressed using the distributive property?

• By using the formula 2 * (length + width).

• By expressing it as a sum of products of dimensions.

• By multiplying the length by the width.

• By adding the lengths of all sides.

What is the result of distributing 8y * 1/2 in the expression?

• 4y

• 8y

• 2y

• 16y

What pattern is observed when averaging numbers around a date on a calendar?

• The average is always zero.

• The average is always an even number.

• The average equals the date itself.

• The average is always a prime number.

Why does the algebraic pattern with the calendar work?

• Because of the associative property of multiplication.

• Because of the cancellation of opposite numbers.

• Because of the commutative property of addition.

• Because of the reflexive property of equality.

What is the relationship between subtraction and addition emphasized in the lesson summary?

• Subtracting a number is the same as dividing by one.

• Subtracting a number is the same as adding its opposite.

• Subtracting a number is the same as adding zero.

• Subtracting a number is the same as multiplying by zero.

In the homework, how should you rewrite the expression 20 - 9 + 8 - 7 using only addition?

• 20 + (-9) + 8 + (-7)

• 20 + 9 + 8 + 7

• 20 - 9 - 8 - 7

• 20 + 9 - 8 + 7