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hundred cans, what was his profit if he sold the mustard at 10 cents a can ?

9. A box filled with sand is 16 feet long, 10 feet wide, and 16 inches deep. If sand weighs 165 pounds to the cubic foot,

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what is the weight of the contents of the box ? Give the answer in tons.

10. A rainfall of one inch amounts to how many gallons of water to the acre ? to how many tons ?

11. If the rainfall on a certain day in Virginia City, Nevada, was 2.25 inches, find the number of cubic feet that fell on a lot 209 feet square. Find the number of gallons.

Measures of Weight

Avoirdupois
16 Ounces (oz.) =1 Pound (lb.

2000 Pounds 1 Ton (T.) 2240 pounds is called a long ton. It is used in the custom house, and where coal and ore are handled.

Avoirdupois weight is used for most commodities in common use except gold and silver.

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Troy
24 Grains (gr.) = 1 Pennyweight (pwt.)
20 Pennyweights = 1 Ounce (oz.)
12 Ounces = 1 Pound (lb.)

1 lb. = 12 oz. - 240 pwt. = 5760 gr. A carat is about 3.2 Troy grains, and is used in weighing diamonds.

Troy weight is used for weighing gold, silver, diamonds, and other precious minerals.

The avoirdupois pound contains 7000 grains; the Troy pound, 5760 grains.

Apothecaries
20 Grains (gr.)= 1 Scruple (sc.)
3 Scruples = 1 Dram (dr.)
8 Drams = 1 Ounce (oz.)
12 Ounces = 1 Pound (lb.)

Apothecaries' weight is used by druggists and physicians in compounding and prescribing medicines.

Measures of Time

60 Seconds (sec.)= 1 Minute (min.)
60 Minutes

1 Hour (hr.)
24 Hours

= 1 Day (da.) 7 Days

1 Week (wk.) 365 Days

1 Common Year (yr.) 366 Days

= 1 Leap Year 100 Years

= 1 Century (Cent.)

Circular Measures

60 Seconds (")=1 Minute ()
60 Minutes = 1 Degree o
360 Degrees = 1 Circumference (circ.)

This table is used in measuring angles, and in reckoning latitude and longitude.

Difference in Time

Difference in time is the interval between two specified dates.

YEAR

MONTH

DAY

EXAMPLE 1. Find the difference in time between March 6, 1904, and August 15, 1916.

August 15, 1916, is set down as the 15th

day of the 8th month of the year 1916. Simi1916 8 15

larly March 6, 1901, is set down as the 6th 1904 3 6

day of the 3d month of the year 1904. 12 5 9

By subtraction, the difference in time is seen to be 12 years, 5 months, and 9 days.

EXAMPLE 2. Find the difference in time between Dec. 11, 1900, and June 24, 1916.

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As the number of the month in the subtrahend is greater than that in the minuend, diminish the number of the year by 1 and increase the number of the month by 12. Subtract as before and the difference is seen to be 15 years, 6 months, and 13 days.

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Exercise

1. How many days from May Day to Christmas ?

2. How many days from Memorial Day to Independence Day?

3. How many days from Lincoln's Birthday to Independence Day ?

4. How many days from Washington's Birthday to Thanksgiving Day in the current year ?

5. How many days from the first day of spring to the first day of winter ?

6. How many days from Christmas to the Fourth of July ?

7. Find the difference in time between Nov. 23, 1875, and Dec. 11, 1900.

8. Find the time interval between Oct. 10, 1845, and March 6, 1904.

9. Find the time between June 11, 1840, and Dec. 8, 1870. 10. If the Panama Pacific Exposition opened Feb. 20, 1915, and closed Dec. 4 of the same year, how long was it open ?

Longitude and Time The longitude of a place is its distance in degrees east or west of an established meridian, sometimes called the prime meridian. The meridian through Greenwich, England, is ordinarily used as the prime meridian.

Rule. — To find the difference in longitude between two places, subtract if both are east or both are west of an established meridian ; if one is east and the other west, add.

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