Add and subtract whole numbers: word problems
key notes:
| Understanding Addition and Subtraction in Word Problems |
- Addition is used when we want to find the total or combine quantities.
- Subtraction is used when we want to find how much is left or the difference between quantities.
Keywords to look for:
| Operation | Keywords |
|---|---|
| Addition | total, in all, altogether, combined, sum, more |
| Subtraction | left, remaining, difference, fewer, less, decrease |
| Steps to Solve Word Problems |
- Read the problem carefully to understand what is being asked.
- Identify the numbers and operation (addition or subtraction).
- Write the number sentence (equation).
- Solve step by step.
- Check your answer to ensure it makes sense.
- Write the answer with the correct unit (like books, rupees, km, etc.).
| Examples |
Example 1 – Addition:
A shop has 245 pencils. The shop receives 180 more pencils. How many pencils are there now?
Solution:
245+180=425
✅ Answer: 425 pencils
Example 2 – Subtraction:
Ravi had ₹500. He bought a book for ₹175. How much money is left?
Solution:
500−175=325
✅ Answer: ₹325
Example 3 – Combination Problem:
A library had 750 books. It bought 230 more books and gave 120 books to another school. How many books are there now?
Solution:
750+230=980(after buying)
980−120=860(after giving away)
✅ Answer: 860 books
| Tips for Solving Word Problems |
- Read carefully and underline important numbers.
- Identify the operation needed before calculating.
- Break large numbers into smaller parts if needed.
- Always write the answer with the unit.
| Practice Questions |
- A school had 620 notebooks. It received 345 more. How many notebooks does the school have now?
- A farmer had 950 oranges. He sold 475 oranges. How many oranges are left?
- A car travels 245 km on Monday and 310 km on Tuesday. How far did it travel in total?
- A library had 1200 books. It bought 350 more and gave 200 books to students. How many books are there now?
- A shop has 780 candies. 265 candies are sold. How many candies remain?
Answers:
- 965 notebooks
- 475 oranges
- 555 km
- 1350 books
- 515 candies
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: 916340300Perform 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!
