# Short rules of arithmetic for farmers

The following was taken from a book inherited from Gene Carlson’s great-grandfather.
1. How to find the number of tons of hay in a mow
Multiply the length of the mow in feet, by the width in feet, and that by the height in feet, and divide the result by 400 if the hay is well settled (or by 500 for new hay) and you have the number of tons in the mow.
2. How to find the number of tons of hay in a stack
Let the hay settle 30 days. Then measure over the stack with a tape line from ground to ground in feet and then find the width of the stack in feet and add the two results together and divide the sum by four.
Then multiply this result by itself, and multiply that number by the length of the stack in feet, and divide the product by 400 (or, for greater accuracy, by 420) and you will have the number of tons in the hay stack.
3. How to measure ear corn in a crib
Multiply the length in feet by the height in feet, and that again by the width in feet, and multiply the result by four (or for good, sound corn well settled, by five). Then cut off the right-hand figure and you have the contents in bushels of shelled corn.
When the crib is flared at the side, find the average width by adding together the top and bottom widths and dividing by two.
4. How to find the number of bushels of grain in a box or bin
Multiply the length in feet by the height in feet, and that again by the breadth in feet and then again by eight, and cut off the right-hand figure. The result will be the number of bushels.
6. How to find the number of heaped bushels of ear corn, apples, or potatoes in a crib
Multiply the length in feet by the breadth in feet, and that again by the height in feet and multiply the result by six, cut off the right-hand figure, and you have the number of heaped bushels.
7. How to find the contents of a wagon box
Multiply the depth of the wagon box in inches by two, and you have the number of bushels. A common wagon box is a little more than 10 feet long and three feet wide, and will hold about two bushels for every inch in depth.
If the wagon box is 11 feet long, multiply the depth in inches by two and add one-10th of the number of bushels to itself.
8. How to find the weight of cattle by measurement
Multiply the distance around the animal (back of the fore-shoulder) in feet by itself, and then multiply that result by 17.5 and you have the weight of the animal very near.
For more accurate results, instead of multiplying by 17.5, multiply by five times the length of the animal in feet (measuring from the fore-part of the should blade to the bone at the tail, in a vertical line with the buttocks) and divide this product by 1.5 for average cattle (very fat by 1.425; very lean by 1.575) and you have the dressed weight of the animal.
9. How to find the price per hundred when sold by the ton.
If the cistern or tank is square, multiply the height width and depth in feet together and divide the product by four, and the result will equal the number of barrels the cistern will hold.
If the cistern or tank is round, multiply the diameter in feet by itself and multiply that by the depth in feet, and divide the product by five and you will have the number of barrels the cistern or tank will hold.
11. How to find the contents of barrels and casks
Add together the diameters at the bung and head in inches and divide the sum by two, and the result will be the average diameter. Now multiply this result by itself, and multiply the product by the length of the barrel or cask, in inches.
Multiply this result again by 34, and cut off the four right-hand figures and you will have the number of gallons.
12. Gross and net weight of hogs
It is assumed that the gross weight of hogs diminished 1/5 or 20 percent of itself, give the net weight and the net weight increases by 1/4 or 25 percent of itself equals the gross weight.
Thus: If the gross weight of a load of hogs is 1,800 pounds, the net weight would be 1/5 or 360 less, or 1,440 pounds. If the net weight is 1,440, the gross weight will be 1/4 or 360 pounds more, or 1,800 pounds.
13. How to find the number of yards of carpet to cover a floor
Multiply the length of the room in feet by the width in feet and divide the results by nine, and you have the number of yards of carpet required, if the carpet is one yard wide.
If the carpet is only 3/4 of a yard wide, proceed as above, and then multiply by four and divide by three.
14. An easy way to multiply by 11
To multiply any two figures by 11, add the two figures together and place their sum between the two figures of that number. If the sum of the two figures exceed nine, the left-hand figure must be increased by one.
15. How to find the number of acres in a field
If the field is rectangular, multiply the length in rods by the breadth and divide by 160.
If the piece is triangular, multiply the length in rods by the breadth and divide by two. Then divide by 160 and the result will be the number of acres in the field.
1. Example how many acres in a piece of land 90 rods long and 20 rods wide? 80×20=1600; 1600 divided by 160=10 acres.
2. Example how many acres in a triangular field 80 rods long and 40 rods wide: 80×40 divided by two=1,600 sq. rods; 1600 divided by 160=10 acres.
16. How to measure wood
Multiply the length, breadth, and height in feet together, and divide by 128. The result will be the number of cords.
Example: How many cords in a pile of wood 20 feet long, four feet wide, and eight feet high? 20x4x8=640; 640 divided by 128=five cords.
17. How to find the number of shingles required for a roof
Multiply the length of the roof by twice the length of one rafter, and multiply the result by eight if the shingles are to be exposed 4.5 inches to the weather, or by seven if the shingles are to be exposed five inches.
And presto, you will have the number of shingles required.