Common Mistakes: Time and Money
Why Learn About Mistakes?
Everyone makes mistakes when learning something new. When you know about common mistakes, you can avoid them! Let's look at mistakes students often make with time and money.
Common Mistakes with Telling Time
Mistake 1: Mixing Up the Clock Hands
The Mistake: Thinking the long hand shows the hour.
Why It Happens: The long hand is bigger, so some students think it shows the bigger number (hour).
The Fix: Remember: Short hand = Hour. The word "short" and "hour" both have an "o" sound!
Correct: Short hand on 5, long hand on 12 = 5 o'clock
Mistake 2: Reading the Wrong Number
The Mistake: When the short hand is between two numbers, reading the wrong one.
Why It Happens: The short hand moves slowly between numbers as the hour passes.
The Fix: Look at which number the short hand just passed. That's the hour!
Correct: If short hand is between 3 and 4 (closer to 3), it's after 3 o'clock.
Mistake 3: Forgetting "O'clock"
The Mistake: Saying "It's 4" instead of "It's 4 o'clock."
Why It Happens: Students see the number and just say it.
The Fix: When the long hand points to 12, always say "o'clock" after the number!
Correct: "The time is 4 o'clock."
Common Mistakes with Counting Money
Mistake 4: Confusing Coin Values
The Mistake: Thinking a nickel is worth more than a dime because it's bigger.
Why It Happens: A nickel is larger in size than a dime, so it seems like it should be worth more.
The Fix: Remember: Size doesn't matter for coin value! A small dime (10 cents) is worth more than a big nickel (5 cents).
Correct: Penny (1 cent) < Nickel (5 cents) < Dime (10 cents) < Quarter (25 cents)
Mistake 5: Counting Coins by How Many, Not Value
The Mistake: Saying "I have 3 coins" instead of counting the value.
Why It Happens: Students count the number of coins, not what they are worth.
The Fix: Always count the value of each coin, not just how many coins you have.
Correct: 1 dime + 2 pennies = 10 + 1 + 1 = 12 cents (not "3 cents")
Mistake 6: Forgetting to Add All the Coins
The Mistake: Skipping a coin when counting.
Why It Happens: When there are many coins, it's easy to miss one.
The Fix: Line up your coins. Touch each one as you count. Move coins aside after counting them.
Correct: Touch and count: "10... 15... 16... 17" (1 dime, 1 nickel, 2 pennies)
Mistake 7: Starting with Small Coins
The Mistake: Counting pennies first, then nickels, then dimes.
Why It Happens: Students start with the first coin they see.
The Fix: Always start with the biggest value coins first! It makes counting easier.
Correct: Start with quarters (25), then dimes (10), then nickels (5), then pennies (1).
Practice: Spot the Mistake!
Can you find the mistake in each problem?
Problem 1
Sam says: "The clock shows the long hand on 3, so it's 3 o'clock."
What's wrong?
Show Answer
Sam looked at the wrong hand! The short hand shows the hour, not the long hand. He should look at where the short hand points.
Problem 2
Amy has 1 dime and 1 nickel. She says she has 2 cents.
What's wrong?
Show Answer
Amy counted the number of coins (2 coins) instead of the value. A dime = 10 cents and a nickel = 5 cents. She really has 15 cents.
Problem 3
The short hand is between 8 and 9, and the long hand is on 12. Jake says it's 9 o'clock.
What's wrong?
Show Answer
Jake read the number the short hand is going toward, not the one it passed. Since the hand is between 8 and 9, and the long hand is on 12, it's 8 o'clock (the hour just passed).
Problem 4
Lily says: "A nickel is worth more than a dime because it's bigger."
What's wrong?
Show Answer
Coin size does not equal coin value! A nickel is bigger in size but worth less. A dime (10 cents) is worth more than a nickel (5 cents).
Problem 5
Tim counted: "1 penny, 2 pennies, 3 pennies, 1 nickel, 2 nickels." He says he has 5 cents.
What's wrong?
Show Answer
Tim counted the total number of coins (5) instead of the total value. 3 pennies = 3 cents, 2 nickels = 10 cents. He really has 13 cents.
Problem 6
Mia says "It's 6" when looking at a clock with short hand on 6 and long hand on 12.
What could be better?
Show Answer
Mia should say "It's 6 o'clock." When the long hand points to 12, we say "o'clock" after the hour.
Problem 7
Ben counts his coins: "1 penny is 1 cent, 1 nickel is 5 cents, so I have 6 cents." But he forgot he also has a dime.
What's the real total?
Show Answer
Ben forgot to count the dime! 1 dime = 10 cents, 1 nickel = 5 cents, 1 penny = 1 cent. Total = 16 cents.
Problem 8
Sara counts: "1 penny... 2 pennies... 3 pennies... 1 dime." She says 13 cents.
Is she right? What could she do better?
Show Answer
Sara got the right answer (13 cents), but she should start with the dime first! Counting "10... 11... 12... 13" is easier than counting pennies first.
Check Your Understanding
Question 1
Which hand on the clock shows the hour?
Show Answer
The short hand shows the hour.
Question 2
True or False: A bigger coin is always worth more money.
Show Answer
False! A nickel is bigger than a dime, but a dime is worth more (10 cents vs 5 cents).
Question 3
When counting coins, should you start with the biggest or smallest coins?
Show Answer
Start with the biggest coins first (quarters, then dimes, then nickels, then pennies).
Next Steps
- Review any mistakes you've made before
- Practice slowly and carefully
- When you're ready, take the Unit Quiz!