Add and subtract whole numbers: word problems

key notes :

1.Understanding the Problem

  • Read Carefully: Teach students to read the word problem carefully and more than once to ensure they understand what is being asked.
  • Identify Keywords: Look for keywords that indicate whether to add or subtract.
    • Addition Keywords: Sum, total, in all, combined, together, plus, increase.
    • Subtraction Keywords: Difference, how many more, less, decrease, remain, subtract, minus.

2. Identify the Operation

  • Determine the Operation: Decide whether the problem requires addition or subtraction based on the keywords and context.
    • Example: “If you have 150 apples and you give away 45, how many do you have left?” – This requires subtraction.

3. Breaking Down athe Problem

  • Underline Key Information: Highlight or underline the numbers and important details in the problem.
  • Write Down the Equation: Translate the word problem into a mathematical equation.
    • Example: “Maria has 120 stickers. She buys 35 more. How many stickers does she have now?”
      • Equation: 120+35=155

4. Solving the Problem

  • Perform the Calculation: Add or subtract the numbers as required by the problem.
  • Double-Check: Encourage students to check their work to ensure the calculation is correct.

5. Answer the Question

  • Complete the Answer: After solving the equation, ensure students answer the question in the context of the problem.
    • Example: “Maria has 155 stickers now.”

6. Practice with Examples

  • Addition Word Problem: “There are 238 students in the school. If 125 more students join, how many students are there in total?”
    • Solution: 238+125=363 students.
  • Subtraction Word Problem: “John had 500 baseball cards. He gave 147 to his friend. How many cards does he have left?”
    • Solution: 500−147=353 cards.

7. Problem-Solving Strategies

  • Estimation: Before solving, estimate the answer to see if your final answer is reasonable.
  • Draw a Picture: Sometimes drawing a picture or using a number line helps visualize the problem.
  • Work Backward: If the problem is complex, start with the final information and work backward to figure out what is needed.

8. Multi-Step Word Problems

  • Multiple Operations: Some word problems require both addition and subtraction (or multiple additions/subtractions).
    • Example: “Sarah bought 3 packs of pencils with 12 pencils each. She gave 15 pencils to her friend. How many pencils does she have now?”
      • Solution: First, find the total pencils: 3×12=36.
      • Then subtract: 36−15=21 pencils.

Learn with an example

🗼 Newberg Paper Company just sent 21,273 cases of paper to a customer. Of those cases, 8,957 cases have lined paper. The rest have unlined paper.

How many cases have unlined paper?

​_______ cases

  • Subtract the number of cases of lined paper from the total number of cases.
  • Subtract:
  • Subtract the ones. You need to carry over first. Subtract 13 − 7.
  • Subtract the tens. Subtract 6 − 5.
  • Subtract the hundreds. You need to carry over first. Subtract 12 − 9.
  • Subtract the thousands. You need to carry over first. Subtract 10 − 8.
  • Subtract the ten thousands.
  • The difference is 12,316. 12,316 of the cases are unlined paper.

🗼 A carnival makes most of its money from the bumper cars and the horse race game. Last year, it pulled in ₹87,420 from the bumper cars and ₹38,139 from the horse race game. In all,

how much did those two games make?

₹______

  • Add the amounts of money.
  • Add:
  • 87,420 + 38,139 =
  • Add the ones. Add 0 + 9.
  • Add the tens. Add 2 + 3.
  • Add the hundreds. Add 4 + 1.
  • Add the thousands. Add 7 + 8. Remember to carry over.
  • Add the ten thousands. Add 1 + 8 + 3.
  • The sum is 125,559. The carnival made ₹125,559 from those two games.

🗼 Since he was hired, a chef has served a total of 63,259 guests. Of those guests, 12,673 were adults.

How many children has the chef served?

​ ______ children

  • Subtract the number of adults served from the total number of guests.
  • Subtract:
  • 63,259 – 12,673 =
  • Subtract the ones.
  • Subtract the tens. You need to carry over first. Subtract 15 − 7.
  • Subtract the hundreds. You need to carry over first. Subtract 11 − 6.
  • Subtract the thousands. Subtract 2 − 2.
  • Subtract the ten thousands.
  • The difference is 50,586. The chef has served 50,586 children.

Let’s practice!