5th Grade - Math

LESSON PROBLEM: Analysis: What proportion of rough rice is prepared into consummable rice?


When rice is harvested from the fields or paddies, each grain itself is enclosed in a rough, straw-like outer hull. In this form it is called "rough rice" or "paddy rice." The inedible hull is removed by a shelling machine. The grains can then be packaged as brown rice, or they can be further milled or polished into white rice by rubbing the bran layer off.

White rice goes through a few processing steps before it reaches a boiling pot in your kitchen. What happens to the hull and bran of milled white rice? Is it waste? What is the yield of white rice from a given quantity of rough rice? Below is a table showing an analysis in processing 100 pounds of rough rice.

100 lbs rough rice

80 lbs brown rice

20 lbs hulls

70 lbs white rice                                    

10 lbs byproducts
55 lbs whole head rice

15 lbs broken rice

7 lbs bran 3 lbs polish
10 lbs large second 5 lbs. brewer's broken pieces

After the shelling of 100 pounds of rough rice, 20 pounds of hulls are left which are not edible. These hulls are used in a variety of ways, including being burned for fuel and as bedding for livestock. The remaining 80 pounds of rice are left to be polished into white rice. Resulting from this process are 10 pounds of byproducts: bran and polish (the inner thinner layers of bran). Both of these are usable as ingredients in cereals, baking mixes and as feed for animals. Polish is high in vitamins and can also be used as an ingredient in baby foods and vitamin products. The 70 pounds of white rice is further divided by a series of screens and separated by the size of the pieces of the grain. Fifty five pounds of the rice is whole kernel or head rice which is the white rice which goes to markets in the U.S. and abroad. It is also sold to cereal and soup suppliers. The remaining 15 pounds are broken pieces of rice. The bigger pieces, called second heads and screenings are used in processed rice products like baby foods, cereal and other products. The finer broken pieces, called brewers rice, are used to make rice flour and to brew beer.

The table above shows what percentage of the whole, each form of rice results from the original 100 pounds of rough rice.

What percent of the original yield is whole white rice?
The table shows us that 55 percent is whole white rice.

What percent is inedible hull?
Twenty percent is inedible hull.

With a little math we can figure other percentages represented by the table.

What percentage of broken rice is brewer's rice? We are asking, what percentage of 15 is 5?
X% of 15 = 5     X% = 5/15       X = 33%

What percentage of brown rice turns into a byproduct as it is converted to white rice?
X% of 70 = 10   X% = 10/170   X = 14%


Write three word problems based on the table in the study guide.


Do research on wheat cultivation and processing and create a product porportions table like the one for rice in the study guide.

  • byproduct
  • bran
  • hull
  • feed
  • thresh
  • proportion

Click here to play Rice Rampage!
How is Rice Grown:
Farming rice is hard work. Click here to learn more about the Stages of Farming Rice.
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