Add and subtract whole numbers: word problems

key notes:

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:

  • Addition Example: Sarah has 125 apples and buys 86 more. How many apples does she have now?
    • Solution: 125+86=211125 + 86 = 211125+86=211
  • Subtraction Example: John has 500 marbles and gives away 143. How many marbles does he have left?
    • Solution: 500−143=357500 – 143 = 357500−143=357

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
    1. Set up the addition problem:
       Population in 1990:       906450600
   Increase in population:  +  9889700
            --------------------------
   Total population in 1991: 916340300

    2. Perform the addition:

    • Add the numbers column by column, starting from the rightmost digit and moving left, carrying over if necessary.
    1. 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:

    1. Identify the numbers involved:
    • The sum of two numbers: 41482308
    • One of the numbers: 3918695

    2. Set up the subtraction problem:

       Sum of two numbers:       41482308
   One number:             -  3918695
            --------------------------
   Second number:            37563613
    1. Perform the subtraction:
    • Subtract the numbers column by column, starting from the rightmost digit and moving left, borrowing if necessary.

    4.Write the result:

    • The other number: 37,56,36,13

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

    Let’s practice!