« PreviousContinue »
Or, in measuring boards, you may multiply the length in feet by the breadth in inches, and divide by 12, the quotient will give the answer in square feet, &c.
Thus, in the foregoing example, 21X18+12=31,5 as before.
4. If a board be 8 inches wide, how much in length will make a square foot ?
Rule.--Divide 144 by the breadth, thus, 8)144
Ans. 18 in. 5. If a piece of land be 5 rods wide, how many rods in length will make an acre ?
RULE.—Divide 160 by the breadth, and the quotient will be the length required, thus, 5) 160
Ans. 32 rods in length. ART. 3, To measure a triangle Definition.-A triangle is any three cornered figure which is bounded by three right lines.*
RULE. Multiply the base of the given triangle into half its perpendicular height, or half the base into the whole perpen dicular, and the product will be the area.
1. Required the area of a triangle wnose base or longest side is 32 inches, and the perpendicular height 14 inches.
32x7=224 square inches the answer. 2. There is a triangular or three cornered lot of land whose base or longest side is 51; rods; the perpendicular from the corner opposite the base measures 44 rods ; how many acres doth it contain ?
51,5X22=1133 square rods, Tacres, 13rods.
* A Triangle may be either right angled or oblique ; in either case the teacher can easily give the scholar a right idea of the base and perpendicular, by marking it down
late, paper &c.
TO MEASURE A CIRCLE. Art. 4. The diameter of a Circle being given, to find the Circumference.
RULE. As 7 : is to 22 : : so is the given diameter : to the circumference. Or, more exactly, as 113 : is to 355 : &c. the diameter is found inversely.
Nore.--The diameter is a right line drawn across the Circle through its centre.
EXAMPLES. 1. What is the circumference of a wheel whose diameter is 4 feet ?-as 7 : 22 : : 4 : 12,57 the circumference.
2. What is the circumference of a circle whose diameter, is 35 ?--As 7 : 22 : : 35 : 110 Ans.—and inversely as 22 : 7 : : 110 : 35, the diameter, &c. ART. 5. . To find the area of a Circle.
RULE. Multiply half the diameter by half the circumference, and the product is the area ; or if the diameter is given without the circumference, multiply the square of the diaméter by ,7854 and the product will be the area.
EXAMPLES. 1. Required the area of a circle whose diameter is 12 hghes, and circumference 37,7 inches.
18,85=half the circumference.
6=half the diameter.
113,10' area in square inches. 2. Required the area of a circular garden whose diameter is 11 rods ?
,7854 By the second method, 11X11
Ans. 95,0334 rods. SECTION 2. OF SOLIDS. Solids are estimated by the solid inch, solid foot, &c. 1728 of these inches, that is 12x12x12 make 1 cubic or solid foot.
ART. 6. To measure a Cube. Definition.--A cube is a solid of six equal sides, each of which is an exact square.
RULE. Multiply the side by itself, and that product by the same side, and this last product will be the solid content of the cube.
1. The side of a cubic block being 18 inches, or 1 foot and 6 inches, how many solid inches doth it contain ? ft. in. ft. 1
6=1,5 and 1,5X1,5X1,5=3,375 solid feet. Ans. Or, 18x18x18=5832 solid inches, and 1=3,375.
2. Suppose a cellar to be dug that sliall contain 12 teet every way, in length, breadth and depth ; how many solid feet of earth must be taken out to complete the same ?
12x12x12=1728 solid feet, the Ans. ART. 7. To find the content of any regular solid of three
dimensions, length, breadth and thickness, as a piece of timber squared, whose length is more than the breadth and depth.
RULE. Multiply the breadth by the depth, or thickness, and that product by the length, which gives the solid content.
1. A square piece of timber, being one foot 6 inches, or 18 inches broad, 9 inches thick, and 9 feet or 108 inches long; how many solid feet doth it contain ?
1 ft. 6 in=1,5 foot, 9 inches
Prod. 1,125x9=10,125 solid feet, the Ans.
in. in. in. solid in. Or, 18X9X108=17496--1728=10,125 feet.
But, in measuring timber, you may multiply the breadth in inches, and the depth in inches, and that product by the length in feet, and divide the last product by 144, which will give the solid content in feet, &c.
2. A piece of timber being 16 inches broad, 11 inches thick, and 20 feet long, to find the content ?
Breadth 16 inches.
Prod. 176x20=3520 then, 3520-144=24,4 feet,
the Answer. 3. A piece of timber 15 inches broad, 8 inches thick, and 25 feet long; how many solid feet doth it contain ?
Ans. 20,8+feet. ART. 8. When the breadth and thickness of a piece of
timber are given in inches, to find how much in length will make a solid foot.
RULE. Divide 1728 by the product of the breadth and depth, and the quotient will be the length making a solid foot.
EXAMPLES 1. If a piece of timber be 11 inches broad and 8 inches deep, how many inches in length will make a solid foot ?
11x8=88)1728(19,6 inches. Ans. 2. If a piece of timber be. 18 inches broad and 14 in ches deep, how many inches in lengʻ i will make a solid foot ? 18X14=252 divisor, then 252,1728(6,8 inches. Ans.
Art. 9. To measure a Cylinder. Definition.-A Cylinder is a round body whose bases are circles, like a round column or stick of timber, of equil bigness from end to end.
RULE. Multiply the square of the diameter of the end by ,7854 which gives the area of the base ; then multiply the arta of the base by the length, and the product will be the solid content.
EXAMPLE What is the solid content of a round stick of timber of equal bigness from end to end, whose diameter is 18 inches, and length 20 feet ?
18 in. 1,5 ft.
Square 2,25X,7854=1,76715 area of the base
x 20 length.
Ans. 35,34300 solid content. Or, 18 inches.
324x,7854*254,4696 inches area of the base.
20 length in feet.
144)5089,3920(35,343 solid feet. Ans. Art. 10. To find how many solid feet a round stick of
timber, equally thick from end to end, will contain when
RULE. Multiply twice the square of its semi-diameter in inches by the length in feet, then divide the product by 144, and the quotient will be the answer.
EXAMPLE If the diameter of a round stick of timber be 22 inches and its length 20 feet, how many solid feet will it contain when hewn square ?
11X11X2X20---144=33,6+ feet, the solidity when hewn square. ART. 11. To find how many feet of square edged boards
of a given thickness, can be sawn from a log of a given diameter.
RULE. Find the solid content of the log, when made square, by the last article— Then say, 'As the thickness of the board including the saw calf : is to the solid feet : : so is 12 (inches) to the number of feet of boards.
many feet of square edged boards, 11 inch thick, inclading the saw calf, can be sawn from a log 20 feet long and 24 inches diameter ?
12x12x2x20;144540 feet, solid content.
As 1 : 40 : : 12 : 384 feet, the Ans