Ounces and Pounds and Tons... Oh My!

Lesson Plan - Get It!

Audio:

• How much do you weigh?

Your scale probably measures your weight in pounds. In the United States, we use three different units to measure weight. We use different units to measure objects with different sizes. Weight is measured using ounces, pounds, and tons.

• An ounce (oz.) is the smallest unit of mass. One ounce weighs about the same as one slice of bread.
• A pound (lb.) is the same as 16 ounces. We use pounds to measure our own weight. A football or a baseball weighs about one pound.
• We can use tons to weigh very heavy objects. In some countries, one ton equals 2,240 pounds, but in the United States, one ton is the same as 2,000 pounds. A small car weighs around one ton. A blue whale can weigh up to 150 tons!

Compare ounces, pounds, and tons, when you read US Standard Mass (Weight) by MathIsFun.com.

On a sheet of paper, create your own weight conversion chart.

• How many ounces are in one pound?
• How many pounds are in one ton? Include the following conversions:
• 1 ounce = 16 pounds
• 2,000 pounds = 1 ton

We can use conversions to change one unit to another.

If one pound equals 16 ounces, then how many ounces are in 1 pound 4 ounces?

• 16 ounces = 1 pound
• 16 ounces + 4 ounces = 20 ounces
• There are 20 ounces in 1 pound 4 ounces.

How can we convert 5 pounds into ounces?

We know there are 16 ounces in one pound, so we can multiply 5 pounds by 16:

• 5 pounds x 16 ounces = 80 ounces
• There are 80 ounces in 5 pounds.

• How do you think we would convert pounds to tons?

Take a moment to try an example:

• How do you express 6,000 pounds in tons?

• What is your answer?

If you said 3 tons, you’re right!

You can use repeated subtraction:

• There are 2,000 pounds in 1 ton:
  • 6,000 - 2,000 = 4,000
  • 4,000 - 2,000 = 2,000
• You can count up by 2,000:
  • 2,000 + 2,000 = 4,000
  • 4,000 + 2,000 = 6,000
• You can divide 6,000 by 2,000:
  • 6,000 ÷ 2,000 = 3 tons

• Which method did you use to solve the problem?
• If you made a mistake, do you see where you went wrong?

• When would you use ounces in real life?
• When would you use pounds?
• Can you think of a time when you needed to weigh something on a scale? Did you use ounces or pounds?

Discuss your ideas with a parent or teacher.

Now, go to the Got It? section and use your conversion chart to complete a measurement activity.