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# Wheat and chessboard problem – Wikipedia

mathematical problem 2 5 − 1 { \textstyle 2^ { 5 } -1 } By the fourth dimension that the fifth public square is reached on the chessboard, the board contains a total of 31, or, grains of wheat. The wheat and chessboard problem ( sometimes expressed in terms of rice grains ) is a numerical problem expressed in textual shape as :

If a chessboard were to have pale yellow placed upon each square such that one grain were placed on the first square, two on the irregular, four on the one-third, and therefore on ( doubling the total of grains on each subsequent squarely ), how many grains of pale yellow would be on the chessboard at the finish ?

The problem may be solved using elementary addition. With 64 squares on a chessboard, if the count of grains doubles on consecutive squares, then the sum of grains on all 64 squares is : 1 + 2 + 4 + 8 + … and so away for the 64 squares. The entire number of grains can be shown to be 264-1 or 18,446,744,073,709,551,615 ( eighteen quintillion, four hundred forty-six quadrillion, seven hundred forty-four trillion, seventy-three billion, seven hundred nine million, five hundred fifty-one thousand, six hundred and fifteen, over 1.4 trillion measured tons ), which is over 2,000 times the annual universe production of wheat. [ 1 ] This drill can be used to demonstrate how cursorily exponential sequences grow, arsenic well as to introduce exponents, zero ability, capital-sigma notation and geometric serial. Updated for modern times using pennies and a conjectural interrogate such as “ Would you rather have a million dollars or a penny on day one, doubled every day until day 30 ? “, the formula has been used to explain colonial matter to. ( Doubling would yield over one billion seventy three million pennies – or over 10 million dollars : 230-1=1073741823 ). [ 2 ] [ 3 ]

## Origins

The problem appears in different stories about the invention of chess. One of them includes the geometric progress problem. The report is first known to have been recorded in 1256 by Ibn Khallikan. [ 4 ] Another version has the inventor of chess ( in some tellings Sessa, an ancient indian Minister ) request his rule give him wheat according to the wheat and chessboard problem. The rule laughs it off as a meager prize for a brainy invention, only to have court treasurers report the unexpectedly huge number of wheat grains would outstrip the ruler ‘s resources. Versions differ as to whether the inventor becomes a high-level adviser or is executed. [ 5 ] Macdonnell besides investigates the earlier development of the theme. [ 6 ]

[ According to al-Masudi ‘s early history of India ], shatranj, or chess was invented under an indian king, who expressed his preference for this game over backgammon. [ … ] The Indians, he adds, besides calculated an arithmetical progress with the squares of the chessboard. [ … ] The early affection of the Indians for enormous calculations is well known to students of their mathematics, and is exemplified in the writings of the great astronomer Āryabaṭha ( wear 476 A.D. ). [ … ] An extra argument for the amerind origin of this calculation is supplied by the Arabic name for the squarely of the chessboard, ( بيت, “ beit ” ), ‘house ‘. [ … ] For this has undoubtedly a historical connection with its indian appointment koṣṭhāgāra, ‘store-house ‘, ‘granary ‘ [ … ] .

## Solutions The sum of powers of two from zero up to a given incontrovertible integer world power is 1 less than the adjacent office of two ( i.e. the following Mersenne number The simple, brute-force solution is merely to manually double and add each step of the series :

deoxythymidine monophosphate 64 { \displaystyle T_ { 64 } } where deoxythymidine monophosphate 64 { \displaystyle T_ { 64 } }

The serial may be expressed using exponents :

T 64 = 2 0 + 2 1 + 2 2 + ⋯ + 2 63 { \displaystyle T_ { 64 } =2^ { 0 } +2^ { 1 } +2^ { 2 } +\cdots +2^ { 63 } } and, represented with capital-sigma note as :

∑ iodine = 0 63 2 i. { \displaystyle \sum _ { i=0 } ^ { 63 } 2^ { iodine } .\, } It can besides be solved much more well using :

T 64 = 2 64 − 1. { \displaystyle T_ { 64 } =2^ { 64 } -1.\, } A validation of which is :

second = 2 0 + 2 1 + 2 2 + ⋯ + 2 63. { \displaystyle s=2^ { 0 } +2^ { 1 } +2^ { 2 } +\cdots +2^ { 63 }. } Multiply each side by 2 :

2 sulfur = 2 1 + 2 2 + 2 3 + ⋯ + 2 63 + 2 64. { \displaystyle 2s=2^ { 1 } +2^ { 2 } +2^ { 3 } +\cdots +2^ { 63 } +2^ { 64 }. } Subtract original series from each side :

2 south − second = 2 64 − 2 0 { \displaystyle 2s-s=2^ { 64 } -2^ { 0 } } ∴ south = 2 64 − 1. { \displaystyle \therefore s=2^ { 64 } -1.\, } The solution above is a particular case of the kernel of a geometric series, given by

a + a r + a r 2 + a gas constant 3 + ⋯ + a roentgen n − 1 = ∑ k = 0 normality − 1 a gas constant kilobyte = a 1 − roentgen n 1 − gas constant, { \displaystyle a+ar+ar^ { 2 } +ar^ { 3 } +\cdots +ar^ { n-1 } =\sum _ { k=0 } ^ { n-1 } ar^ { k } =a\, { \frac { 1-r^ { north } } { 1-r } }, } where a { \displaystyle a } is the first gear term of the serial, r { \displaystyle r } is the common ratio and nitrogen { \displaystyle n } is the count of terms. In this problem a = 1 { \displaystyle a=1 } , r = 2 { \displaystyle r=2 } and normality = 64 { \displaystyle n=64 } . The exercise of working through this problem may be used to explain and demonstrate exponents and the promptly growth of exponential and geometric sequences. It can besides be used to illustrate sigma notation. When expressed as exponents, the geometric series is : 20 + 21 + 22 + 23 + … and thus away, up to 263. The base of each exponentiation, “ 2 ”, expresses the doubling at each square, while the exponents represent the position of each square ( 0 for the first public square, 1 for the irregular, and sol on. ). The count of grains is the sixty-fourth Mersenne number .

## moment half of the chessboard An example of Ray Kurzweil ‘s moment half of the chessboard principle. The letters are abbreviations for the SI metric unit prefixes In engineering scheme, the “ moment one-half of the chessboard ” is a phrase, coined by Ray Kurzweil, [ 7 ] in mention to the point where an exponentially growing gene begins to have a significant economic affect on an organization ‘s overall clientele scheme. While the number of grains on the first half of the chessboard is large, the sum on the second half is vastly ( 232 > 4 billion times ) larger. The phone number of grains of wheat on the first half of the chessboard is 1 + 2 + 4 + 8 + … + 2,147,483,648, for a sum of 4,294,967,295 ( 232 − 1 ) grains, or about 279 tonnes of wheat ( assuming 65 magnesium as the mass of one grain of wheat ). [ 8 ]

The number of grains of wheat on the second half of the chessboard is 232 + 233 + 234 + … + 263, for a full of 264 − 232 grains. This is equal to the square of the number of grains on the first half of the display panel, plus itself. The first square of the irregular half alone contains one more grain than the stallion first half. On the 64th square of the chessboard alone, there would be 263 = 9,223,372,036,854,775,808 grains, more than two billion times arsenic many as on the inaugural half of the chessboard. On the integral chessboard there would be 264 − 1 = 18,446,744,073,709,551,615 grains of pale yellow, weighing about 1,199,000,000,000 metric tons. This is about 1,645 times the global output of wheat ( 729,000,000 metric unit tons in 2014 and 780.8 million tonnes in 2019 ). [ 9 ]

## use

Carl Sagan titled the second chapter of his final book The Persian Chessboard and wrote that when referring to bacteria, “ Exponentials ca n’t go on everlastingly, because they will gobble up everything. ” [ 10 ] Similarly, The Limits to Growth uses the narrative to present propose consequences of exponential growth : “ exponential emergence never can go on identical long in a finite outer space with finite resources. ” [ 11 ]

## References

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