Add and subtract whole numbers: word problems
key notes:
| đ1. Understanding Word Problems |
- Word Problems: Problems presented in a narrative form that require translating the words into mathematical operations.
- Purpose: Helps students apply their arithmetic skills to real-world scenarios and improves problem-solving abilities.
| đ Steps to Solve Word Problems |
Read the Problem Carefully:
Identify key information: Look for numbers, keywords, and what the problem is asking.
- Example: “Sarah has 125 apples and she buys 78 more. How many apples does she have now?”
Determine the Operation Needed:
Addition: When combining quantities or finding the total.
- Keywords: “total,” “in all,” “together,” “combine,” “sum.”
Subtraction: When finding the difference or removing part of a quantity.
- Keywords: “difference,” “how many more,” “how many less,” “left,” “subtract.”
Write an Equation:
Translate the word problem into a mathematical equation using the appropriate operation.
- Example: “Sarah has 125 apples and buys 78 more” translates to 125+78.
Solve the Equation:
Perform the arithmetic operation (addition or subtraction) to find the answer.
- Example: 125+78=203
Check the Answer:
Review the problem and the solution to ensure the answer makes sense in the context of the question.
- Example: After solving 125+78=203, check if 203 apples makes sense given the problem.
| đ Types of Word Problems |
Addition Word Problems:
Example: “Tom has 42 marbles. His friend gives him 37 more marbles. How many marbles does Tom have now?”
- Solution: 42+37=79
Subtraction Word Problems:
Example: “Lily had 89 pencils. She gave 23 pencils to her friend. How many pencils does Lily have left?”
- Solution: 89â23=66
Mixed Operations:
Example: “There are 56 students in a classroom. If 12 students leave and then 15 more students join, how many students are in the classroom now?”
- Solution: First, subtract 56â12=44, then add 44+15=59.
| ⨠Tips for Solving Word Problems |
- Highlight Key Information: Underline or circle important numbers and words in the problem.
- Break Down the Problem: Divide the problem into smaller, manageable parts if needed.
- Use Drawings or Models: Visual aids can help illustrate the problem and assist in solving it.
- Check Units: Ensure that units (e.g., apples, pencils) are consistent and make sense with the answer.
| â¨Practice Problems |
Addition Problem:
Problem: “Emma has 143 stickers. She buys a pack with 89 more stickers. How many stickers does she have in total?”
- Solution: 143+89=232
Subtraction Problem:
Problem: “A library had 500 books. 176 books were checked out. How many books are left in the library?”
- Solution: 500â176=324
Mixed Operation Problem:
Problem: “At a party, there were 125 balloons. 30 balloons popped, and 15 new balloons were added. How many balloons are there now?”
- Solution: First, subtract 125â30=95, then add 95+15=110
| đ Common Mistakes to Avoid |
- Misreading the Problem: Ensure you understand what is being asked before solving.
- Incorrect Operations: Use addition or subtraction based on the context of the problem.
- Forgetting to Check: Always review your solution to make sure it fits the context of the problem.
Learn with an example
Word problems on adding of large numbers:
The population of the country in 1990 was 906450600 and the next year it increased by 9889700.
What was the population of that country in the year 1991?
The population of a country in 1990 = 90,64,50,600
Increased population by next year = + 98,89,700
Total population of that country in 1991 = 91,63,40,300
Therefore, the population of that country in the year of 1991 is 91,63,40,300.
đĽA chocolate factory usually makes 6,444 chocolates per month. In the month before Valentine’s Day, it makes 6,364 more than that.
How many chocolates does the factory produce in that month?
â____ chocolates
- Add the numbers of chocolates.
Add:
- Add the ones. Add 4 + 4.
- Add the tens. Add 4 + 6. Remember to carry over.
- Add the hundreds. Add 1 + 4 + 3.
- Add the thousands. Add 6 + 6.
- The sum is 12,808. The factory produces 12,808 chocolates in that month.
đĽA treasure hunter discovered a buried treasure chest. He opened it up and discovered that it contained 4,534 diamonds and 1,083 rubies.
How many gems were in the chest?
â______ gems
- Add the number of diamonds and the number of rubies.
Add:
- Add the ones. Add 4 + 3.
- Add the tens. Add 3 + 8. Remember to carry over.
- Add the hundreds. Add 1 + 5 + 0.
- Add the thousands. Add 4 + 1.
- The sum is 5,617. There were 5,617 gems in the chest.
Kimi painted her house using 9,308 litres of white paint and 9,035 litres of sea green paint.
How many litres of paint in all did Kimi use?
â_______ litres
- Add the numbers of litres.
Add:
9,308 + 9,035 = ___,_____
- Add the ones. Add 8 + 5. Remember to carry over.
- Add the tens. Add 1 + 0 + 3.
- Add the hundreds. Add 3 + 0.
- Add the thousands. Add 9 + 9.
- The sum is 18,343. Kimi used 18,343 litres of paint in all.
Let’s practice!
