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9. The wall of a town is 25 feet high, which is surrounded by a moat of 30 feet in breadth, I defire to know the length of a ladder that will reach from the outside of the moat to the top of the wall,
Ans. 39,05 feet.
The hypothenufe and perpendicular given to find the bafe. Rule. The square root of the difference of the squares of the hypothenuse and perpendicular is the length of the base.
The base and hypothenuse given to find the perpendicular. Rule. The square root of the difference of the hypothenuse and base is the heighth of the perpendicular.
N. B. The two last questions may be varied for examples to the two last propositions.
Any number of men being given to form them into a square battle, or
to find the number of ranks and files. RULE. The square root of the number of men given, is the num. ber of men either in rank or file.
An army consisting of 331776 men, I desire to know how many in rank and file ?
II. A certain square pavement contains 48841 square stones, all of the same size, I demand how many are contained in one of the fides,
EXTRACTION OF THE CUBE ROOT.
TO extract the Cube Root is to find out a number which being multiplied into itself, and then into that product, produceth the given number.
Rule. Point every third figure of the cube given, beginning at the unit's place, seek the greatest cube to the first point and subtract it therefrom, put the root in the quotient, and bring down the figures in the next point to the remainder for a resolvend.
Find a divisor by multiplying the square of the quotient by 3. See how often it is contained in the resolvend, rejecting the units and tens, and put the answer in the quotient.
3. To find the fubtrahend. 1. Cube the last figure in the quotient. 2. Multiply all the figures in the quotient by 3, except the laft, and that product by the square of the last. 3. Multiply the divisor by the last figure. Add these products together, gives the subtrahend, which subtract from the resolvend ; to the remainder bring down the next point and proceed as before. Roots.
3. 4. 5.
9. CUBES, 8. 27. 64. 125. 216. 343. 512: 729.
What is the cube root of 99252847
64=Cube of 4.
216=Cube of 6.
27=Cube of 3.
=Divifor x by 3. 1916847 Subtrahend.
Another new and more concise method of extracting the Cube Root.
RULE. 1. Point every third figure of the cube given, beginning at the unit's place, then find the nearest cube to the first point, and subtract it therefrom, put the root in the quotient, bring down the figures in the next point to the remainder for a resolvend.
2. Square the quotient and triple the square for a divisoras 4X4X3=48. Find how often it is contained in the resolvend, reječting units and tens, and put the answer in the quotient.
3. Square the last figure in the quotient, and put it on the right hand of the divisor :
As 6X6=36 put to the divisor 48=4836. 4. Triple the last figure in the quotient, and multiply by the former, put it under the other, units under the tens, add them together, and multiply the sum by the last figure in the quotient, subtract that product from the resolvend, bring down the next point and proceed as before.
Anf. 73. Ans. 179. Anf. 319. Anf. 439.
Square of 4X3=48 Divisor. 99252847(463
5556 X 6 = 33336 Square of 46=2116X3=6348 Divisor Square of 3=9 put to 6348=*631809 1916847
3X3 X 46=414
638949X3=1916847 What is the cube root of 389017? 3.
What is the cube root of 5735339 ? 4. What is the cube root of 32461759 ? 5. What is the cube root of 84604519 ? 6. What is the cube root of 259694072 ?
Ans. 638. 7.
What is the cube root of 48228544 ?
What is the cube root of 22069810125? Anf. 2805.
Ans. 6031. What is the cube root of 673373097125? Ans. 8765 When the given number consists of a whole number and decimal together, make the number of decimals to consist of
3, 6, 9, &c. places, by adding cyphers thereto, fo that there may be a point fall on the unit's place of the whole number. 13.
What is the cube root of 12.977875 ? 14
What is the cube root of 36155.027576? Ans. 33,06+ 15.
What is the cube root of ,001906624? 16. What is the cube root of 33:230979637 ?
Anf. 3,215+ 17. What is the cube root of 15926,972504?
Anf. 25,19+ is. What is the cube root of ,053258279 ?
Anf. ,376 +
To extra&t the Cube Root of a Vulgar Fraction. Rule. Reduce the fraction to its lowest terms, then extract the Gube root of the numerator and denominator for a new numerator and denominator, but if the fraction be a surd, reduce it to a decimal, and then extract the root from it.
EXAMPLES. 19. What is the cube root of ?
* When the quotient is 2 or 3 there must be a cypher put to supply the place of tens,
21. What is the cube root of 8?
Ans. ' .
SURDS. What is the cube root of 4 ? 23. What is the cube root of ? 24. What is the cube root of ?
To extraet the Cube Root of a mixt number. RULE. Reduce the fractional part to its lowest terms, and then the mixt number to an improper fraction, extract the cube roots of the numerator and denominator for a new numerator and denominator ; but if the mixt number given be a surd, reduce the fractional part to a decimal, annex it to the whole number, and extract the root there. from.
EXAMPLES. 25. What is the cube root of 12 ??
Anf. 21. 26. What is the cube root of 31 32 ?
Ans. 3. 27. What is the cube root of 405 15?
SURDS. 28. What is the cube root of 7} ?
Anf. 1.93+ 29. What is the cube root of g ?
Ans. 2,092+ 30. What is the cube root of 8??
Anl. 2,057+ THE APPLICATION. If a cubical piece of timber be 47 inches long, 47 inches broad, and 47 inches deep, how many cubical inches doth it contain ?
Anf. 103823 2. There is a cellar dug that is 12 feet every way, in length, breadth and depth, how many solid feet of earth were taken out of it ?
Ans. 1728. 3. There is a stone of a cubic form, which contains 389017 solid feet, what is the superficial content of one of its fides ?
Between two numbers given, to find two mean proportionals. Rule. Divide the greater extreme by the lesser, and the cube root of the quotient multiplied by the lesser extreme, gives the lesser meant; multiply the said cube root by the lesser mean, and the produet will be the greater mean proportional.
Anf. 18 and 54. 5. What are the two mean Proportionals between 4 and 108 ?
Ans. 12 and 36.
To find the side of a cube that shall be equal in folidity to any givens
Solid, as a globe, cylinder, prism, cone, &c. Rule. The cube root of the solid content of any solid body given is the side of the cube of equal folidity.
EXAMPLE. 6. If the solid content of a globe is 10648, what is the side of a cube of equal folidity ?
The side of the cube being given, to find the side of that cube, that shall
be double, treble, &c. in quantity to the given cube. Rule. Cube the side given, and multiply it by 2, 3, &c. the cube root of the product is the side fought.
EXAMPLE. 7. There is a cubical vessel, whose fide is r2 Inches, and it is required to find the side of another vessel, that is to contain 3 times as niuch ?
EXTRACTION OF THE .BIQUADRATE ROOT.
To extract the Biquadrate Root is to find out a number, which being involved four times into itself, will produce the given number.
Rule, First extract the Square Root of the given number, and then extract the Square Root of that Square Root, and it will give the Biquadrate Root required.
EXAMPLES. 1. What is the biquadrate of 27 ?
Anf. 531441 What is the biquadrate of 76 ?
33362176 3. What is the biquadrate of 275 ?
5719140625 4. What is the biquadrate root of 5314417
27 5 What is the biquadrate root of 33362176 ?
76 What is the biquadrate root of 5719940625 ? 275