Simple Interest Problems Answer Key for 1st Grade Students

Introduction to basic money concepts and financial literacy with detailed solutions and explanations.

Problem Solutions: 1 to 3
1 Savings Problem
Problem 1
Sarah has $5 in her piggy bank. She adds $2 more. How much money does she have?
🐷
$5 + $2
Solution: $7
Problem type:

Simple addition: Adding money amounts together.

Solution method:
  1. Identify starting amount: $5 in piggy bank
  2. Identify added amount: $2 added
  3. Add amounts: $5 + $2 = $7
  4. State answer: Sarah has $7 total
Step 1: Read the problem carefully

Sarah starts with $5 and adds $2 more.

Step 2: Identify the operation

We need to add the amounts together.

Step 3: Perform the calculation

$5 + $2 = $7

Step 4: Write the final answer

Sarah has $7 in total.

Answer: $7
Correct answer:

Sarah has $7 in her piggy bank.

Applied rules:

• Addition: When combining money amounts

• Total: Sum of all amounts

• Units: Keep units consistent (dollars)

2 Earnings Problem
Problem 2
Tom earned $3 for helping his mom. Then he earned $4 more for helping his dad. How much did he earn total?
😊
$3 + $4
Solution: $7
Problem type:

Simple addition: Adding earnings from different sources.

Step 1: Identify first amount

Tom earned $3 for helping mom.

Step 2: Identify second amount

He earned $4 for helping dad.

Step 3: Add the amounts

$3 + $4 = $7

Step 4: State the total

Tom earned $7 total.

Answer: $7
Correct answer:

Tom earned $7 in total.

Applied rules:

• Combining earnings: Add amounts from different sources

• Total calculation: Sum all individual amounts

• Unit consistency: All amounts in dollars

3 Growth Problem
Problem 3
Jake had $10 in his bank. After one year, it grew to $12. How much did it grow?
💰
$10
Starting amount
📈
$12
After growth
✅
$2
Growth amount
Problem type:

Simple subtraction: Finding the difference between amounts.

Step 1: Identify starting amount

Jake started with $10.

Step 2: Identify final amount

After growth, he had $12.

Step 3: Calculate the difference

$12 - $10 = $2

Step 4: State the growth

The money grew by $2.

Answer: $2
Correct answer:

The money grew by $2.

Applied rules:

• Subtraction: Find difference between amounts

• Growth calculation: Final amount minus initial amount

• Positive result: Money increased

Answer Key Information
💰 + 💰 = Total 💰
Money Addition Formula
Addition
💰 + 💰 = Total
Combine money amounts
Subtraction
Final - Initial = Change
Find differences
Total
All amounts combined
Sum of all money
➕
Addition
When combining money
➖
Subtraction
When finding differences
📊
Growth
Money increasing over time
Key definitions:

Answer key: Solutions to problems with detailed explanations

Simple interest: Basic concept of money growing over time

Principal: The original amount of money

Growth: Increase in money amount

Solution methods:
  1. Read carefully: Understand what the problem asks
  2. Identify amounts: Find all money amounts mentioned
  3. Choose operation: Determine if adding or subtracting
  4. Calculate: Perform the mathematical operation
  5. Check answer: Verify it makes sense
Tip 1: Always read the problem completely before solving.
Tip 2: Look for key words like "total," "more," or "grew."
Tip 3: Check your answer by working backwards.
Tip 4: Keep track of units (dollars, cents).
Common error: Forgetting to include all amounts mentioned.
Key insight: Money problems use basic arithmetic operations.
Problem Solutions: 4 to 5
4 Bank Growth Problem
Problem 4
Emma put $20 in the bank. After saving for a year, she had $25. How much did she earn?
🏛️
$25 - $20
Solution: $5
Problem type:

Simple subtraction: Finding earnings from growth.

Step 1: Identify initial amount

Emma started with $20.

Step 2: Identify final amount

After saving, she had $25.

Step 3: Calculate the difference

$25 - $20 = $5

Step 4: State the earnings

Emma earned $5 from saving.

Answer: $5
Correct answer:

Emma earned $5 from saving.

Applied rules:

• Subtraction: Find difference between amounts

• Earnings calculation: Final amount minus principal

• Positive result: Money increased through saving

5 Goal Achievement Problem
Problem 5
Max wants to buy a toy that costs $15. He has $8 saved. How much more does he need?
🎯
$15
Goal amount
💰
$8
Current savings
✅
$7
Amount needed
Problem type:

Simple subtraction: Finding the difference to reach a goal.

Step 1: Identify the goal

Max needs $15 for the toy.

Step 2: Identify current amount

He has $8 saved.

Step 3: Calculate the difference

$15 - $8 = $7

Step 4: State the amount needed

Max needs $7 more to buy the toy.

Answer: $7
Correct answer:

Max needs $7 more to buy the toy.

Applied rules:

• Subtraction: Find difference between goal and current amount

• Goal calculation: Amount needed = Goal - Current

• Planning: Determine how much more is needed

Solution Principles & Methods
💰 + Time = More 💰
Money Growth Principle
🔍
Read Carefully
Understand what the problem asks
📝
Write Down
Note all important amounts
🧮
Calculate
Perform the right operation
✅
Check
Verify your answer makes sense
Key definitions:

Simple interest: Basic concept of money growing over time

Principal: The original amount of money

Earnings: Money gained through saving

Growth: Increase in money amount

Goal: Target amount to achieve

Solution methods:
  1. Read the problem: Understand what is being asked
  2. Identify amounts: Find all relevant money amounts
  3. Choose operation: Determine if adding or subtracting
  4. Perform calculation: Do the math carefully
  5. Verify answer: Check if it makes logical sense
Tip 1: Always include units (dollars) in your answer.
Tip 2: Draw pictures or use real coins to visualize problems.
Tip 3: Break complex problems into smaller steps.
Tip 4: Practice with real-life scenarios to build understanding.
Common error: Mixing up addition and subtraction operations.
Key insight: Most money problems use basic arithmetic.
Solution principles:

• Read problems carefully to understand what is being asked

• Identify all relevant money amounts

• Choose the correct mathematical operation

• Perform calculations accurately

• Verify that your answer makes sense

• Include appropriate units in your final answer

Questions & Answers

Question: How do I know when to add or subtract money?

Answer: Here's how to decide:

  • Add when: You're combining amounts, getting more money, or finding totals
  • Subtract when: You're finding differences, calculating growth, or seeing what's left
  • Look for clues: Words like "total," "combined," "more" suggest addition
  • Look for clues: Words like "difference," "how much more," "left" suggest subtraction

Always read the problem carefully to understand what it's asking!

Question: How can I help my child check their money problem answers?

Answer: Here are effective checking strategies:

  1. Work backwards: Use the answer to see if it makes sense with the problem
  2. Estimate: Check if the answer is reasonable
  3. Use manipulatives: Count real coins or bills to verify
  4. Re-read: Make sure the answer addresses the question asked
  5. Double-check: Repeat the calculation to ensure accuracy

Encourage your child to always check their work before moving on.

Question: What are the most important money concepts for 1st graders to master?

Answer: Essential money concepts for 1st graders:

  • Basic counting: Counting coins and bills
  • Addition/subtraction: Combining and comparing amounts
  • Value recognition: Understanding different denominations
  • Simple saving: Concept that money can grow over time
  • Goal setting: Saving for specific purposes
  • Problem solving: Using math to solve money questions

These foundational concepts prepare them for more complex financial learning.