Learning Mathematics - Activities for the Grocery Store: Grades 3-4 (page 4)

Mathematics at the Grocery Store — Activities

The grocery store is one of the best examples of a place where the ability to use mathematics is put to work in the "real world." It's a great place to practice measurement and estimation and to learn about volume and quantity and their relationships to the sizes and shapes of containers—geometry!

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Weighing In    Check It Out    Put It Away

Weighing In
Grades 3-4

		In many schools, children learn the metric system of meters, grams and liters, along with the more familiar system of feet, ounces and gallons. Practicing measurement both ways helps children learn both systems.

Grocery shopping offers opportunities for children to increase their estimation and measurement skills by choosing and weighing fruit and vegetables.

What You Need

• A grocery scale

What to Do

• In the produce section of the store, explain to your child that what you pay for fruit and vegetables is based, in large part, on the quantity you buy and what it weighs—that produce is usually sold for a certain amount per pound. Tell her that pounds are divided into smaller parts called ounces, and it takes 16 ounces to make one pound. Show her the scale that is used to weigh produce.
• Gather the produce you want to buy and ask your child to weigh a few items. Then have her estimate the weight of another item before she weighs it. If you need one pound of apples, ask her to place several apples on the scale and then estimate how many apples she will have to add or take away to make one pound.
• Let your child choose two pieces of fruit, such as oranges. Have her hold one piece in each hand and guess which weighs more. Then have her use the scale to see if she is right.
• Ask your child questions such as the following to encourage her to think about measurement and estimation:
  • Will six potatoes weigh more or less than the six oranges?
  • Which has more potatoes, a pound of big ones or a pound of little ones?
  • How much do potatoes cost for each pound? If they cost 10 cents per pound, what is the total cost of the six potatoes?
• If your child knows the metric system (and the scale has a metric range), have her weigh items in grams and kilograms. Ask her to find out the following:
  • How a kilogram compares to a pound.
  • How many grams an apple weighs.
  • How many kilograms (or kilograms plus grams) a sack of potatoes weighs.
  • Which contains more apples, one pound or one kilogram?
  • Which weighs more, one pound apples or one kilogram of apples?

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Check It Out
Grades 3-4

		Grocery shopping can be a good place to show children a practical use for calculators—for example, as a way to keep a running total of what the groceries cost.

The checkout lane of a grocery store can be a good place for children to practice using mental math by estimating the cost of groceries and figuring out change.

What to Do

• As you wait in a grocery checkout lane, use the time to have your child estimate what the total cost of your groceries will be. Tell him that one easy way to estimate a total is to round off numbers. That is, if an item cost 98 cents, round it off to $1. Explain that the answer he gets won't be the exact cost, but it will be about that. Tell him that the word about shows that the amount you say is just an estimate.
• Using the estimated total, ask your child: "If the groceries cost $16 and I have a $20 bill, how much change should the checker give back to me? If the cost is $17.25, what coins is she likely to give me?
• At the checkout counter, ask your child to watch as the items are rung up. What's the actual total cost of the groceries? How does this amount compare to the estimate? When you pay for the items, will you get change back from your $20 bill, or will you have to give the checker more money?
• If you receive change, have your child count it to make sure the amount is correct.

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