Students use food and farming as a basis for exploring the concepts of estimating and measuring using customary and metric units of measurements. Grades 3-5

bushel: a unit of measurement used in US agriculture that is equivalent to a volume of 64 pints, but is generally standardized by weight for different products; a bushel of wheat weighs 60 lbs, a bushel of corn weighs 56 lbs

capacity: the maximum amount that something can contain

customary: a system of measurement used in the United States that includes units for measuring length, capacity, and weight

estimation: a rough calculation of the value, number, quantity, or extent of something

gallon (gal): a unit of volume for liquid measure equal to four quarts

gram (g): a metric unit of mass equal to one thousandth of a kilogram (kg)

liter (L): metric unit for measuring liquid volume, equal to 1000 milliliters (ml)

measurement: the size, length, or amount of something while using a customary unit for measuring

metric: a system of measurement based on multiples of ten that is used throughout the world

pint (pt): a unit of liquid or dry capacity equal to one half of a quart

pound (lb): the customary unit of measurement for weight, equal to 16 ounces (oz)

volume: the amount of space an object occupies

weight: a measurement indicating how heavy something is

This lesson provides students with an opportunity to practice measuring weight and volume in the metric and customary systems. The metric system is based on units of ten and is used globally, while the customary system is used primarily in the United States. Estimation is an important skill for making rough calculations when precise measurement isn't practical. Students should be able to estimate both capacity (volume) and weight using metric and customary units.

The materials for this lesson are easily obtained; most can be pulled from recycling bins or found at a grocery store. Empty food containers like cereal boxes, cottage cheese tubs, and beverage bottles are the least expensive math manipulative you can find! Plastic and metal containers should be washed before use (do not use packaging that contained raw meat; it can spread unwanted bacteria). In this lesson, students' experience measuring the weight and volume of food items will help them gain an understanding of how estimation and measurement skills are used on the farm.

Being able to measure in a variety of ways is a valuable life skill. How many times a day are we asked, or do we ask, “How much?” “How big?” “How far?” Many of our measurements are based on methods that people used before we had standardized devices like yardsticks and rulers. Horses were measured according to how many hands high they were. A yard of fabric was the length of the merchant’s outstretched arm, measured from his or her nose to the tip of his or her thumb. A foot was the length of an average person’s foot. Agricultural products like vegetables and grains are measured in bushels, equivalent to about 35.2 liters. Today, measurements have been widely standardized. A foot or a meter means the same thing everywhere.

Whether you are a student buying an apple for lunch or a farmer selling wheat, you need a way to measure whatever it is you are buying or selling. The cashier at the grocery store probably will weigh your apple to determine how much to charge you. The amount of money a farmer receives for his or her wheat will depend on how many bushels he or she has produced. Some products are sold according to their weight or how heavy they are on a scale. Other products are sold according to volume, which is the space the item takes up in cubic units. Liquid products like milk or juice might be sold by the pint, gallon, or liter. Some food products are priced by the piece no matter how big they are, like cucumbers sold two for $1.00 or red peppers sold for $1.50 each.

Most of the produce you buy in the grocery store—apples, peaches, onion, potatoes, tomatoes, squash, etc.—is sold by the pound. But if you go to a farmer's market or buy the same produce from roadside stands, you may pay for it by the bushel or half-bushel basket. Smaller quantities are measured in quart or pint baskets. Most berries—raspberries, strawberries, blueberries, etc.—are sold by the pint or by the quart. Corn on the cob is generally sold by the dozen. Pumpkins are sorted according to size—miniature, small, medium, large, jumbo. Each pumpkin in a category will cost the same.

The price of a beef steer depends on how much the steer weighs. When a steer is sold, it is weighed on a large livestock scale. The weight is then multiplied by the current market price. If the current market price is $1.50 per pound, and the steer weighs 770 pounds (carcass weight), the value of the steer would be $1155. Market prices are determined by how much of a product is available for sale, how much people are willing and able to pay for the product, and other supply and demand factors. 

Wheat farmers sell their wheat by the bushel which weighs 60 pounds. Like beef, the price of wheat per bushel depends on the current market value. Oats, barley, feed corn, rye, and soybeans are also sold by the bushel. However, the seed the farmer purchases for replanting is priced by the pound. Garden seeds and herbs are sold by the ounce because most gardeners do not need large quantities. There are many units of measurement to fit different needs. Sometimes small units work better than large units, and sometimes it is more convenient to measure volume than to measure weight. In this lesson students will learn measurement and estimation skills using a variety of tools and agricultural products.

1. Fill a glass jar with blueberries. Count the number of blueberries as you place them in the jar and do not reveal this number to your students.
2. Show the students the jar and have them estimate the number of blueberries. Take several guesses from the class.
3. Pour water into the jar and allow it to fill to the top. Have the students examine the jar more closely and make a second estimation of the number of blueberries. Did their original estimation change? Why or why not?
4. Ask the following questions:
   • Why do we estimate measurements? (Estimation gives us an approximate idea of something's weight, volume, length, or mass.)
   • What kinds of estimations would a blueberry farmer use? (pounds of blueberries harvested, inches of rain, etc.)
   • What else can be estimated in the real world? (length of a wall, distance to walk to a friend's house, weight of a backpack full of books, amount of time needed to finish homework, etc.)
   • Why is estimation an important skill? (It is a tool for making quick judgments when it isn't necessary or practical to calculate an exact answer or make an exact measurement. For example, when grocery shopping, items placed in the basket are added up to make sure enough money is available to make the purchase.)
   • What types of estimation do farmers make? (yields of a crop for calculating profit, time to harvest a crop for the best rate of production, pounds of feed for the most efficient weight gain in livestock animals) 
   • How can estimations help make accurate measurements? (Estimations can help judge if the actual measurement is reasonable and accurate.)
5. Tell the students they will be making estimates and taking measurements using food items that farmers produce for us to enjoy as part of a nutritious diet.

Activity 1: Produce Shopping

1. Set up four or five work stations, supplying each with a different kind of produce, a grocery flyer showing prices for each kind of produce, and a small scale that registers ounces and pounds (diet scales or kitchen scales).
2. Divide the class into four or five groups, and assign each group to a work station. Hand out the Produce Shopping activity sheet, one per student. 
3. Review estimating, and discuss why it might be useful in a trip to the grocery store. Share the information found in the Background Agricultural Connections section of the lesson with the students.
4. Ask the students to estimate the weight and cost of the produce and record their estimates on the activity sheet.
5. Next, have them weigh the produce and calculate the cost based on the prices listed in the grocery flyers. If you have metric scales, record these weights or make the conversion with the students. A Customary and Metric Unit Equivalents Guide is provided in the Essential Files for making conversions.
6. Ask the groups to move from station to station until each student group has visited each station.
7. Students should complete the totals on the activity sheet.
8. If all of the totals are not the same, ask the students to discuss possible reasons for the discrepancy. (weights and costs may have been rounded up or down) 
9. Assign each group one type of produce to research how US farmers measure the yield of the products per acre, and have them share with the other student groups. For example, farmers measure the number of bushels of harvested wheat per acre.

Activity 2: Measurement Shopping

1. Set up five work stations, and supply each with the following:
   • Station 1: gallon jug, quart container, liter container, liquid measuring cup, and a bucket of water
   • Station 2: quart container, liter container, pint container, liquid measuring cup, and bucket of water
   • Station 3: box of cereal, popcorn, scale (discuss how to use the type of scale you have provided) and liquid measuring cup
   • Station 4: liquid measuring cup, dry measuring cup, and unpopped popcorn (more than 1 cup)
   • Estimation Station 5: Measure and pour out onto a piece of paper: 1 cup of unpopped popcorn, 1 cup of cereal, 1 teaspoon of salt, and 1 tablespoon of cinnamon. Add a glass of milk to this estimation station; note how much milk you put in the glass to share with the students after they've made their estimates.
2. Divide the class into five groups, and assign each group to a work station. Hand out the Weight and Capacity Shopping activity sheets, one per student.
3. Instruct the students to use the activity sheets to record their findings.
4. Ask the groups to move from station to station until each group has visited each station.
5. After all the groups have finished, discuss the following questions as a class (answers will vary):
   • What did you learn about volume and weight?
   • Are the two related?
   • How difficult was it to measure accurately? How difficult was it to estimate accurately?
   • Why is estimation an important skill?
   • Why is it important to measure accurately?
   • How are farmers from the US able to sell or discuss yields with farmers from other countries?

After conducting these activities, review and summarize the following key concepts:

• Making accurate estimations and measurements are two important elements farmers use to effectively utilize their time, calculate yields, and manage their money.
• Customary and metric units of measurements are used for planting, harvesting, processing, packaging, and selling food items grown by farmers.
• Food items are measured and sold in various ways according to its purpose at the time of purchase.

1. http://www.farmcollector.com/farm-life/measurement-on-the-farm.aspx

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