Evaluating Expressions

Evaluating Expressions

Open Ended

2+x =5

What number is x equal to AND how do you know?

Open Ended

What about m?

10-m=9

Open Ended

Why might we use letters in math? (Think about what we did with them in the last 2 examples)

Open Ended

Sherlyn has $25 dollars. She wants to buy her mom a gift that costs $35. How much more money does she need?

Open Ended

Letters that represent numbers in math problems are called variables. They are called variables because the numbers can vary. What does vary mean?

The most common letters used as variables are x and y.

Open Ended

Sometimes you are told what number each variable equals and you must plug in the right numbers to find the answer.

Ex

Evaluating an Expression

Sometimes you are told what number each variable equals and you must plug in the right numbers to find the answer. This is called evaluating an expression

Example: Solve each expression if a=3 and b=4

2+a (plug in 3 for a) so 2+3 =5

b-2 (plug in 4 for b) so 4-2=2

Multiple Choice

Evaluate if c=2

4+c

• 4

• 5

• 6

• 7

Multiple Choice

Evaluate if c=6

c-3

• 1

• 2

• 3

• 4

Multiple Choice

Evaluate if c=5 and d=2

c-d

• 1

• 3

• 5

• 7

Multiple Choice

Evaluate if c=4 and d=3

c-d

• 1

• 3

• 5

• 7

Multiple Choice

Evaluate if a=3

2a

• 5

• 6

• 10

• 12

Multiple Choice

Evaluate if b=2

4b-1

• 6

• 7

• 8

• 9

Multiple Choice

Evaluate if p=2 and q=4

3p+2q

• 6

• 8

• 14

• 16