Subtraction problems involve finding the difference between two numbers and taking value away from a quantity (e.g. comparing an athletes' times after a race or withdrawing money from a bank account).

Key Words and Phrases

There are a few keywords that you'll often see in subtraction problems:

• FIND THE DIFFERENCE: Find the difference between their ages...

• DECREASE: The value of his car decreased by $700 when he drove it off the lot...

• TAKE AWAY: The baker took away 2 cups of sugar in his recipe for cookies... 

• DEDUCT: Her down payment of $500 was deducted from the final price...

A Problem-Solving Strategy

1. Read the whole problem

2. Develop a strategy by asking--

• What information do I have?
• What information do I need to figure out?
• Which operation will help me figure out that information? (Check keywords)

3. Set up the operation.

4. Solve.

Example

Sam's gross pay is $638 per week. His total deductions amount to $210.  What is his net take-home pay?

Develop a strategy by asking--

• What information do I have? Sam earns $638 per week, but $210 is deducted.
• What information do I need? His net take-home pay after the deduction.
• Which operation will help me figure that out? Subtraction

Strategy: Find the difference between $638 and $210 by subtracting.

Solution:

Sam's net take home pay is $428.

Practice

1. You have $304 in your checking account.  If you write a check for $139, how much is left in your checking account?

2. The seating capacity of the Kingdome in Seattle is 57,748. The seating capacity of Fenway Park in Boston is 34,182. Find the difference between the seating capacity of the Kingdome and that of Fenway Park.

3. The graph below shows the number of months required to recover all interest and principal from the Social Security fund after a person retires. Use this graph for the questions below.

a.  How much longer did it take to withdraw principal and interest in 1992 than it did in 1972?

 

b.  How much longer will it take to withdraw principal and interest in 2032 than it did in 1992?

 

 

4.  The table below shows the cost of two cars and the various options the car buyer wants to have.  Use this table for the questions below.

a. Which of these two cars, fully equipped with all options shown, costs more?

 

b. What is the difference in cost between the two basic cars?