Missing Variables in Equations

Missing Number Problems

Let's look at this story problem:

Natalie picked 38 strawberries on Monday. She picked some more on Tuesday and had a total of 60 strawberries. How many strawberries did she pick on Tuesday?

Solving mising number addition problems

• To find a missing addend, we have to subtract

• Example: to find 7 + _ = 10, we would flip the problem and subtract: 10 - 7 = ?

• Our answer is the missing number

Natalie picked 38 strawberries on Monday. She picked some more on Tuesday and had a total of 60 strawberries. How many strawberries did she pick on Tuesday?

• Write an equation to show how to find the number of strawberries, s, Natalie picked on Tuesday.

• Solve the equation to find the number of strawberries Natalie found on Tuesday.

Let's try another one. This time, try writing the equation by yourself!

Subtraction: Missing Second Number

• The first number in a subtraction problem is called the subtrahend

• If it is missing, we subtract the difference to solve

• Example: 14 - _ = 6: to solve we subtract the difference 14 - 6 = ?

• The answer is our missing number

Seth gathered 83 blueberries to use for baking! He used some to make blueberry muffins and had 17 leftover. How many blueberries did he use to make blueberry muffins?

• Write an equation to show how to find the number of blueberries, b, Seth used to make muffins.

• Solve the equation to find the number of blueberries Seth used to make muffins.

Subtraction: Missing First Number

• The second number in a subtraction problem is called the minuend

• To solve, we must add

• Example: _ - 6 = 3: to solve we add: 6+3 = ?

• The answer is our missing number