5th Grade - Math

LESSON PROBLEM: Measurement: What units and concepts do we use to measure rice?


STUDY GUIDE

Rice is measured in many ways: by the length (or size) of the rice plant or rice grain; by the area needed to grow rice crops; by the weight of how much rice is produced; and by the volume of rice harvested or the number of cups of rice we cook.

Because rice is an international commodity, rice measurements are expressed in two different systems -- the metric system and, for our purposes, the English system. Converting units of measurement from one system to the other is fairly easy using conversion tools.

In this example the U.S. system of measurements will be used, with the metric system measurements in parenthesis (metric).



Different types of rice are categorized according to the length of the rice grain compared to its width. The length (or size) of the rice grain or rice plant is measured in inches and feet (centimeters/meters). A mature rice plant can grow from a rice seed of a fraction of an inch to a rice plant of 24 inches (80 centimeters) to as much as 6 feet (2 meters) tall. Just like you grow from small to tall.

In the United States, more than 3 million acres of land are planted with rice. The area of a field planted with rice is measured in acres (hectares). From geometry we remember that area equals "length X width" and can be expressed in square feet. One acre is equivalent to 43,560 square feet. Historically, an acre was the amount of land a farmer could plow in one day's time using a team of oxen. The metric unit for an area planted with rice -- a hectare -- is almost as big as two football fields.

The package of rice we buy at the grocery store is measured by weight in ounces or pounds (grams). Or, for larger quantities, the weight is measured in hundredweights (metric tons), like the amount of rice that is produced, stored and sold as a commodity. More than 191 million hundredweights (cwt) of rice were produced in the United States in the year 2000. A hundredweight is equal to 100 pounds or 1/20 of a ton.

Volume, or the amount of space an object occupies, such as rice, can be measured in small amounts, by cups or quarts, or in large amounts, like bushels. A bushel is a dry measure (different from liquid measures) that equals 32 quarts. Millions of bushels of rice are harvested each year in the United States. In the rice industry, a bushel of rice equals 45 pounds.

Perhaps the most important measurement of rice for the rice farmer is yield. Yield is the total quantity of rice produced from cultivation. Yield is expressed usually as a ratio: how many pounds/tons per acre. For example, in California some farmers produce as much as 6,840,000 pounds of rice per acre.

No matter how you measure it, rice is a life-sustaining crop!




ACTIVITIES

Using a conversion table like the one below, convert these measurements from the U.S. system to the metric system or vice versa:

1. 1,442,000 hectares is _________________ acres.

2. 10 centimeters is ______________ feet.

3. 9,546,000 metric tons is _____________ U.S. tons.

4. 1 pint of rice is _____________ liters of rice.



5. 2 inches is ___________ centimeters.


METRIC SYSTEM
LENGTH
UnitAbbreviation Number of
Meters
Approximate U.S. Equivalent
kilometerkm1,0000.62 mile
hectometerhm100328.08 feet
dekameterdam1032.81 feet
meterm139.37 inches
decimeterdm0.13.94 inches
centimetercm0.010.39 inch
millimetermm0.0010.039 inch
micrometerµm0.0000010.000039 inch
AREA
UnitAbbreviation Number of
Square Meters
Approximate U.S. Equivalent
square kilometersq km or km21,000,0000.3861 square miles
hectareha10,0002.47 acres
area100119.60 square yards
square centimetersq cm or cm20.00010.155 square inch
VOLUME
UnitAbbreviation Number of
Cubic Meters
Approximate U.S. Equivalent
cubic meterm311.307 cubic yards
cubic decimeterdm30.00161.023 cubic inches
cubic centimetercu cm or
cm3 also cc
0.0000010.061 cubic inch
CAPACITY
UnitAbbreviation Number of
Liters
Approximate U.S. Equivalent
cubic dryliquid
kiloliterkl1,0001.31 cubic yards

hectoliterhl1003.53 cubic feet2.84 bushels
dekaliterdal100.35 cubic foot1.14 pecks2.64 gallons
literl161.02 cubic inches0.908 quart1.057 quarts
cubic decimeterdm3161.02 cubic inches0.908 quart1.057 quarts
deciliterdl0.106.1 cubic inches0.18 pint0.21 pint
centilitercl0.010.61 cubic inch
0.338 fluid ounce
milliliterml0.0010.061 cubic inch
0.27 fluid dram
microliterµl0.0000010.000061 cubic inch
0.00027 fluid dram
MASS AND WEIGHT
UnitAbbreviation Number of
Grams
Approximate U.S. Equivalent
metric tont1,000,0001.102 short tons
kilogramkg1,0002.2046 pounds
hectogramhg1003.527 ounces
dekagramdag100.353 ounce
gramg10.035 ounce
decigramdg0.101.543 grains
centigramcg0.010.154 grain
milligrammg0.0010.015 grain
microgramµg0.0000010.000015 grain
Merriam Webster Dictionary







EXTENDED LEARNING


Make a chart of five U.S. food commodities, including rice (for example, wheat, corn). Then using the resource below and the World Wide Web, find out the United States figures for their yield.

 

Rice: Yield and Production by Class, State, and United States, 1998-2000

Class and State

Yield

Production

1998

1999

2000

1998

1999

2000

 

Long Grain

 

Pounds

Pounds

Pounds

1,000 cwt

1,000 cwt

1,000 cwt

AR

5,740

5,780

6,060

73,644

79,417

71,205

CA

5,570

6,800

7,100

537

340

355

LA

4,530

5,000

5,080

26,727

29,050

23,114

MS

5,800

5,650

5,900

15,544

18,250

12,862

MO

5,200

5,400

5,700

7,280

9,278

9,861

TX

5,610

5,920

6,740

15,598

14,978

14,087

             

US

5,426

5,587

5,680

139,328

191,863

131,484

 

Medium Grain

AR

6,200

6,230

6,300

12,400

15,513

14,679

CA

6,000

7,300

8,000

29,218

32,850

41,040

LA

4,500

5,070

5,150

1,380

775

1,288

MO

5,200

5,400

5,700

156

108

87

TX

5,000

4,900

5,800

250

294

255

             

US

6,616

6,811

7,377

43,404

50,540

57,319

 

Short Grain

AR

4,000

6,200

6,000

80

124

120

CA

5,060

7,000

7,300

1,531

3,500

2,190

             

US

5,185

6,969

7,219

1,711

3,634

2,310

 

All

AR

5,800

5,850

6,100

86,134

95,054

86,004

CA

6,850

7,270

7,950

31,386

36,090

42,585

LA

4,530

5,000

5,080

28,167

30,893

24,402

MS

5,800

5,650

5,900

15,544

18,260

12,802

MO

5,200

5,400

5,700

7,436

9,936

9,918

TX

5,600

5,900

6,700

15,846

15,272

14,342

             

US

5,663

5,866

6,278

184,443

206,027

191,113





VOCABULARY
  • hectare
  • acre
  • ton
  • metric
  • volume
  • ratio
  • aggregate
  • measurement
  • commodity
  • yield


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