Coins are part of your life. You use them to buy things. Or maybe you just save them in a bank. Knowing about coins in real life helps you understand multiplication. When you understand how to solve coin problems, you can deal with the amount of items you buy and how much you spend.
Let's first write number families for sentences. Write two variables (letters) and a number. Remember, the word after "each" is a lesser (smaller) number.
Each nickel is worth 5 cents.
The word following "each" is "nickel." So nickel is the lesser number. The other lesser number is 5. That's how much each nickel is worth. Cents is the greatest (larger) number. That's how many cents we have in all. This is what the number family looks like.
Here's a new family: Each quarter is worth 25 cents. One of the lesser numbers is the word following "each." It's "quarter." The other lesser number is the cents for each quarter. How many? The answer is 25.
Here's a coin multiplication problem:
We write 5 as the first lesser number because each nickel is worth 5 cents. We use 3 for N because we have 3 nickels. What multiplication problem do we work to figure out the number of cents we have? How many is 5 × 3? The product, or answer, equals 15 cents.
Here's one more:
You know the first lesser number from how much each coin is worth. The first lesser number here is 10 because each dime is worth 10 cents. You know the other lesser number from how many dimes you have. It's 5 because you have 5 dimes. You now solve for the greatest number by solving 10 × 5. That greatest number is the number of cents you have. That's 50 cents!
