Solved Exercises on Addition/Subtraction Problems in Grade 2

Master addition and subtraction problems within 100: two-step problems, comparison problems, missing addends, and problem-solving strategies through these 5 detailed exercises.

Solution: Exercises 1 to 3
1 Two-Step Problems
Exercise 1
Tom has 24 marbles. He finds 15 more in his pocket. Then he gives 8 to his friend. How many marbles does Tom have now?
Definition:

Two-Step Problem: A problem that requires two different operations to solve

Two-Step Problem Method:
  1. Read the problem carefully
  2. Identify what happens first
  3. Solve the first step
  4. Use the result for the second step
  5. State the final answer
Step 1
24 + 15
Step 2
39 - 8
Result
31
Step 1: Find total after finding more marbles

Tom starts with 24 marbles and finds 15 more

24 + 15 = 39 marbles

Step 2: Subtract marbles given to friend

Tom now has 39 marbles and gives 8 away

39 - 8 = 31 marbles

Step 3: State the final answer

Tom has 31 marbles now

31 marbles
Final answer:

Tom has 31 marbles now.

Applied rules:

• Sequential Processing: Solve one step at a time

• Real-World Context: Follow the story in order

• Verification: Check if answer makes sense

24
Initial marbles
+
Finds more
15
Marbles found
=
Total
39
After finding
-
Gives away
8
Given away
=
Final
31
Final amount
2 Comparison Problems
Exercise 2
Sarah has 42 stickers. Emma has 28 stickers. How many more stickers does Sarah have than Emma?
Definition:

Comparison Problem: A problem that asks for the difference between two quantities

Problem
42 - 28
Calculate
14
Step 1: Identify the larger quantity

Sarah has 42 stickers (larger number)

Step 2: Identify the smaller quantity

Emma has 28 stickers (smaller number)

Step 3: Subtract to find the difference

42 - 28 = 14 stickers

Step 4: State the answer in context

Sarah has 14 more stickers than Emma

14 more stickers
Final answer:

Sarah has 14 more stickers than Emma.

Applied rules:

• Comparison Rule: Subtract smaller from larger

• Context Matters: Answer reflects the question asked

• Verification: Check that 28 + 14 = 42

Sarah
42 stickers
Emma
28 stickers
Difference
42 - 28 = 14
3 Missing Addend Problems
Exercise 3
There are 65 students in the school. 37 are boys. How many are girls?
Definition:

Missing Addend: A problem where you know the total and one part, need to find the other part

Total
65
Known Part
37
Unknown Part
65 - 37
Result
28
Step 1: Identify the total amount

There are 65 students in total

Step 2: Identify the known part

37 students are boys

Step 3: Use subtraction to find the missing part

Total - Boys = Girls

65 - 37 = 28 girls

Step 4: Verify the answer

37 boys + 28 girls = 65 total students ✓

28 girls
Final answer:

There are 28 girls in the school.

Applied rules:

• Part-Part-Whole: Total = Part + Part

• Inverse Operation: Use subtraction to find missing addend

• Verification: Check that parts add to whole

Total Students
65
Boys
37
Girls
? = 65 - 37
Rules and methods, laws,...
Total = Part + Part
Part-Part-Whole Relationship
Two-Step
A + B - C
Multiple operations
Comparison
Larger - Smaller
Difference finding
Missing Addend
Total - Known = Unknown
Part finding
Key definitions:

Two-Step Problem: Requires two separate operations to solve

Comparison Problem: Asks for the difference between quantities

Missing Addend: Finding one part when total and other part are known

Problem-Solving: Systematic approach to solving word problems

Problem-Solving Strategy:
  1. Read Carefully: Understand the situation described
  2. Identify Information: Find numbers and what they represent
  3. Determine Operation: Decide whether to add or subtract
  4. Solve Step-by-Step: Calculate carefully
  5. Check Reasonableness: Verify if answer makes sense
Tip 1: Draw pictures or use objects to represent the problem if needed.
Tip 2: Look for keywords like "more," "total," "altogether" (addition) and "less," "left," "difference" (subtraction).
Tip 3: Always write the answer in a complete sentence that addresses the question.
Solution: Exercises 4 to 5
4 Money Problems
Exercise 4
Maya has $45. She spends $18 on a book and $12 on snacks. How much money does she have left?
Definition:

Money Problem: A word problem involving dollars and cents requiring addition/subtraction

Starting Amount
$45
Total Spent
$18 + $12
Amount Left
$45 - $30
Result
$15
Step 1: Identify the starting amount

Maya begins with $45

Step 2: Calculate total amount spent

$18 + $12 = $30 spent in total

Step 3: Subtract total spending from starting amount

$45 - $30 = $15 remaining

Step 4: State the final answer

Maya has $15 left

$15 left
Final answer:

Maya has $15 left.

Applied rules:

• Sequential Operations: Add expenses first, then subtract from total

• Money Context: Include dollar sign in answer

• Verification: Check that $15 + $30 = $45

5 Multi-Step Problems
Exercise 5
A store has 78 toys. They sell 25 on Monday, receive 16 more on Tuesday, and sell 19 on Wednesday. How many toys are left?
Definition:

Multi-Step Problem: A problem requiring multiple operations in sequence

Start
78
Monday
-25
Tuesday
+16
Wednesday
-19
Result
50
Step 1: Start with initial amount

Store begins with 78 toys

Step 2: Subtract Monday sales

78 - 25 = 53 toys after Monday

Step 3: Add Tuesday delivery

53 + 16 = 69 toys after Tuesday

Step 4: Subtract Wednesday sales

69 - 19 = 50 toys remaining

Step 5: State the final answer

There are 50 toys left

50 toys left
Final answer:

There are 50 toys left.

Applied rules:

• Chronological Order: Process events in the order they happen

• Sequential Calculation: Use previous result for next step

• Verification: Check that 78 - 25 + 16 - 19 = 50

Add list of laws, methods, rules, definitions, expressions,.... Generate well SEO title for this section
Total = Known + Unknown
Missing Addend Formula
Key definitions:

Addition: Combining quantities to find a total

Subtraction: Finding the difference or removing a quantity

Comparison: Finding how much more or less one quantity is than another

Multi-Step: Problems requiring more than one operation

Problem-Solving Steps:
  1. Understand: Read the problem carefully and identify what is being asked
  2. Plan: Decide which operations to use and in what order
  3. Solve: Perform the calculations step by step
  4. Check: Verify that your answer makes sense and is reasonable
Tip 1: Circle or underline important numbers in the problem.
Tip 2: Draw a picture or diagram to represent the problem visually.
Tip 3: Always include units (dollars, marbles, etc.) in your answer.
Tip 4: Estimate your answer first to check reasonableness later.
Common errors: Misreading the problem, performing wrong operation, forgetting to carry/borrow.
Exam preparation: Practice multi-step problems, focus on word problem keywords.
Problem Types:

• Join: Something is added (addition)

• Separate: Something is taken away (subtraction)

• Part-Part-Whole: Finding missing parts (addition/subtraction)

• Compare: Finding differences (subtraction)

Exercise with Visualization: Problem Solving Steps
Exercise 6: Problem Analysis
Problem: "Lisa has 45 candies. She eats 12 and gives 8 to her sister. How many does she have left?"

Analysis: Following the problem-solving steps leads to the correct solution.

  • Start with 45 candies
  • Subtract 12 eaten: 45 - 12 = 33
  • Subtract 8 given away: 33 - 8 = 25
  • Final answer: 25 candies left

Questions & Answers

Question: I don't know if I should add or subtract in word problems. How do I decide?

Answer: Look for clue words that tell you what to do:

  • Addition words: total, altogether, combined, in all, more, plus, added to
  • Subtraction words: left, remaining, difference, less, fewer, gave away, spent, how many more
  • Context matters: Getting something means add, losing/giving away means subtract

Example: "Sam had 10 apples and got 5 more" → add (10 + 5)

Example: "Sarah had 15 cookies and ate 6" → subtract (15 - 6)

Always think: Am I getting more or losing some?

Question: How do I solve problems with more than one step? It gets confusing.

Answer: Break multi-step problems into smaller parts:

  • Read carefully: Understand what happens first, then next, then last
  • Solve one step at a time: Don't try to do everything at once
  • Write down results: Keep track of each step's answer
  • Use the result: Take the answer from step 1 and use it in step 2

Example: "You have 20 stickers, get 10 more, then give 5 away"

Step 1: 20 + 10 = 30 stickers

Step 2: 30 - 5 = 25 stickers (final answer)

Work through each event in the order it happens!

Question: When I see "how many more" in a problem, should I add or subtract?

Answer: "How many more" means you need to find the difference between two amounts, so you subtract:

  • "How many more" = find the difference
  • Subtract the smaller number from the larger number
  • Example: "John has 15 books, Mary has 9. How many more does John have?" → 15 - 9 = 6 more

Think of it as: "What do I need to add to the smaller amount to get the larger amount?"

So if John has 15 and Mary has 9, Mary needs 6 more to have the same as John.

The answer is always positive since it's asking for the difference!