Add and subtract whole numbers: word problems

key notes:

Understanding the Basics

Before we dive into word problems, let’s quickly review adding and subtracting whole numbers. Remember to line up the numbers according to their place value (ones, tens, hundreds, etc.) and carry or borrow when needed.

  • Addition: Combining two or more numbers to find their total.
  • Subtraction: Finding the difference between two numbers.
Keywords in Word Problems

Certain words in a word problem give you clues about whether to add or subtract. Look out for these!

Addition Keywords
Subtraction Keywords
Sum
Total
In all
Together
Plus
Increase
Combined		Difference
Less
Minus
Decrease
Fewer
Left
Remain
How many more?

Here is a step-by-step guide on how to solve word problems on addition and subtraction of whole numbers, along with some examples and explanations for each step.

Interpreting the Problem:

Identify whether addition or subtraction is needed based on the context.

Examples:

Understanding the Problem

Word problems require careful reading to identify the relevant information and the mathematical operations needed to solve them.

Here are two examples:

Example 1: Addition

Problem: A country’s population in 1990 was 906450600, and the next year it increased by 9889700. What was the population of that country in the year 1991?

Steps to Solve:

Identify the numbers involved:

  • Population in 1990: 906450600
  • Increase in population: 9889700

Set up the addition problem:

   Population in 1990:       906450600
   Increase in population:  +  9889700
            --------------------------
   Total population in 1991: 916340300

Perform the addition:

  • Add the numbers column by column, starting from the rightmost digit and moving left, carrying over if necessary.
  • Write the result:
  • The total population in 1991: 91,63,40,300

Therefore, the population of the country in 1991 was 91,63,40,300.

Example 2: Subtraction

Problem: The sum of two numbers is 41482308. If one number is 3918695, then find the other number.

Steps to Solve:

Identify the numbers involved:

  • The sum of two numbers: 41482308
  • One of the numbers: 3918695

Set up the subtraction problem:

   Sum of two numbers:       41482308
   One number:             -  3918695
            --------------------------
   Second number:            37563613

Perform the subtraction:
  • Subtract the numbers column by column, starting from the rightmost digit and moving left, borrowing if necessary.

Write the result:

  • The other number: 37,56,36,13

Therefore, the other number is 37,56,36,13.

Practice Problems

Solve the following word problems. Show your work!

  • A bakery sold 245 chocolate chip cookies and 189 oatmeal cookies. What was the total number of cookies sold?
  • A farmer planted 456 apple trees. 128 of the trees did not survive. How many apple trees are still alive?
  • Maria earned $575 last week. She spent $238 on groceries. How much money does she have remaining?
  • A school has 832 students. If 395 are girls, how many are boys?
  • Tom collected 342 seashells on Monday and 289 seashells on Tuesday. How many seashells did he collect altogether?

Let’s practice!