2. According to a well-known legend, the game of chess was invented many centuries ago in northwestern India by a certain sage. When he took his invention to his king, the king liked the game so much that he offered the inventor any reward he wanted. The inventor asked for some grain to be obtained as follows: just a single grain of wheat was to be placed on the first square of the chessboard, two on the second, four on the third, eight on the fourth, and so on, until all 64 squares had been filled. If it took just 1 second to count each grain, how long would it take to count all the grain due to him?

Respuesta :

Answer:

2^64. I know 2^20 is 1048576. Cube that and multiply by 16 or grab a calculator. I'm too lazy to solve this.

The time taken to count all the grain due to him is [tex]2^{64}-1[/tex] or 18,446,744,073,709,551,615 sec .

What is Geometric Progression?

Geometric Progression (GP) is a type of sequence where each succeeding term is produced by multiplying each preceding term by a fixed number, which is called a common ratio. This progression is also known as a geometric sequence of numbers that follow a pattern.

What is sum of Geometric Progression?

. The sum of infinite, i.e. the sum of a GP with infinite terms is [tex]S_{∞} = \frac{a}{(1 - r) }[/tex]such that 0 < r < 1.

The formula used for calculating the sum of a geometric series with n terms is Sn = [tex]\frac{a( r^{n} -1 )}{(r - 1)} ,[/tex] where r ≠ 1.  

According to the question

A chess board has 64 squares and all had been filled with grain

1st squares of chess board has grain = 1 = [tex]2^{0}[/tex]

2nd squares of chess board has grain = 2 = [tex]2^{1}[/tex]

3nd squares of chess board has grain = 4 = [tex]2^{2}[/tex]

4nd squares of chess board has grain  = 8 = [tex]2^{3}[/tex]

so on ..

As this is an Geometric Progression

Where

First term (a) = 1

common ratio (r) = 2

Number of terms = n = 64

Now,  

it took just 1 second to count each grain ,

Time taken to count all  the grains  

By using formula of sum of Geometric Progression  

Sn = [tex]\frac{a( r^{n} -1 )}{(r - 1)} ,[/tex] where r ≠ 1.  

substituting the values in formula

S₆₄ = [tex]\frac{1( 2^{64}-1 )}{(2-1)} ,[/tex]

S₆₄ = [tex]2^{64}-1[/tex]

S₆₄ = 18,446,744,073,709,551,615

Hence, The time taken to count all the grain due to him is [tex]2^{64}-1[/tex] or 18,446,744,073,709,551,615 sec .

To know more about Geometric Progression and sum of Geometric Progression here:

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