The King and the Mathematician

Algebra Level 2

Once a man did a favor to a king that made the king very happy. Out of joy the king told the man to wish for anything and he would be granted. The man wanted to ask for the whole kingdom which was worth 1500 trillion dollars, but obviously that would make the king mad and he would never be granted that wish.

The man who happened to be a mathematician thought a little bit and said the following:

"Bring in a big piece of rug with an 8 × 8 8\times 8 grid in it. Starting from the top left square, put one dollar in that square. Put two dollars in the square next to it and then double of that, four dollars, in the next square and so on. When you reach the end of the first row, continue on to the next row, doubling the amount every time as you move to the next square, all the way until the 6 4 th 64^\text{th} square at the bottom right."

The king thought for a second. The first square will take one dollar, the second two dollars, the third, four dollars, and next 8 dollars, and then 16 dollars, and then 32 dollars, 64 dollars, 128 dollars, 256 dollars, and so on. That's not too bad. I can do it.

The king agreed. What happened next?

The man got 2 8 = 256 2^8 = 256 dollars and was sad that he had not asked for more The man became the new king of the kingdom and the king went bankrupt The man became as wealthy as what the king's left-over was worth The man got 8 8 = 16 , 777 , 216 8^8=16,777,216 dollars and was very happy

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

12 solutions

Sohail Hameed
May 29, 2014

There are 64 squares. In the first square the king puts $1, in the second he puts $2, in the third he puts $4, and so on. In general, in the nth square he puts 2 n 1 2^{n-1} dollars. In the last square which is 63rd square, he puts 2 64 1 = 9 , 223 , 372 , 036 , 854 , 775 , 808 2^{64-1} = 9,223,372,036,854,775,808 dollars.

And the sum of the sequence 1 , 2 , 4 , 8 , 16 , 32 , . . . , 2 n 1 = 2 n 1 1, 2, 4, 8, 16, 32, ..., 2^{n-1} = 2^{n} - 1 , so overall the king would be putting in 2 64 1 = $ 18 , 446 , 744 , 073 , 709 , 551 , 615 2^{64}-1 = \$18,446,744,073,709,551,615 dollars, if he had that kind of money that is (this amount is much higher than the total worth of the kingdom which is 1500 trillion dollars).

Hence the king will go bankrupt way sooner than reaching the last square and the man will be the new king.

The numbers are in a geometric progression...

Capriquorn Drubo
May 30, 2014

The first row has '8' boxes and the last box contain '128' so that lest '7' boxes will be multiply with '128' '7' more times....like ( 128 X 128 X 128 X 128 X 128 X 128 X 128 X 128 = 7.2057594E16)

Marcellus Windley
Dec 10, 2014

We can make the value of the first box =2^0, since the values are in multiples of 2. Write them as exponents to make it simple. Since 2^0=1, 2^1=2 and so on, if we number the boxes horizontally from 0-7, and vertically from 1-8 (for each row), we get in the box in the bottom right corner to be 2^(7*8)=2^56=7.205e16, which is much more than the fortune of the king. the king can't give the mathematician this amount, since he doesn't have it, he'd go bankrupt.

Saurav Zuer
Jul 28, 2014

just watch out the figures and the order the figures are in and you will get the answer. just get the logic. and become a king

Avinash Chaudhry
Jul 27, 2014

Very easy. There are 64 squares. Starting from 2^0 from the start it goes to 2^63, adding all the values in between i.e. 2^0 + 2^1 + 2^2 +................ + 2^63 = 2^64 -1 . Now , 2^10 is 1024 which is nearly one thousand or three 0 s. So, 2^ 60 will have 3 x 6 = 24 zeroes . One trillion is only 12 zeroes. So the value of Gold here, becomes, much more than the worth of King`s Kingdom. So, the King becomes bankrupt much before reaching the last square and the mathematician becomes the King :)

Phạm Sơn
Jun 7, 2014

there are 64 squares, the first square is 2^0, next is 2^1, so the last square is 2^23. sum of 64 squares is (2^n)-1, is larger than 1500 trillion dollars

Manh Nghiem
Jun 2, 2014

This is really easy problem. The mathematician will get: 1 + 2 + 2^2 + 2^3 + ... + 2^63 = 18 446 744 073 709 551 615 dollars

Krishna Garg
Jun 1, 2014

With the 64 squares grid,putting double tthe dollars of the previous one 64th square will have 2raise to power 64-1 that is Us $ 9,223,372,036,854,775,808 when we add up all 64 squares filled with mentioned do;;ars sum will be $ 18,446,744,073,709,551,615 which is huge amount more than the worth of kingdom and king will be bankrupt. K.K.GARG,India

Vipul Johri
Jun 1, 2014

Its logical. No need of solving. See , if the man mathematician wants the whole kingdom desperately, he will do anything to get it, even by tricking the king.

Here comes the question of mathematics

Koushik Paul - 7 years ago
Krit Phuengphan
May 31, 2014

Easy to see ,without calculating what might be confused, by considering the last square at the bottom right. According to the figure, there are 64 small squares; beginning at the top left with 2^0, it then exactly end with 2^63 = (2^60)x(2^3) = (1024^6)x8. So, the king cost about a QUINTILLION dollars on the final time.

Ne-ko Nya
May 30, 2014

guys , i am confuse....by one thing...

1500 trillion = 1500 x 10^(13) = 1.5x10^(16)

i press calculator 2^63 = 9.22x10^(18)

i calculate the summation of the geometric progression a , ar^2 , ar^3 ,........,ar^63 , a=1 , r=2

a(1-r^n)/(1-r)

= 1 [1-2^(63)] / (1-2) = 9.22 x10^(18) = 2^63

i find it awfully weird , then i do summation manually 2^53 + 2^62 +...+ 1 = 2^64

WHY???????????i thought my summation in geometric sequence is correct but i got different answer when i sum manually......

n is 64 so the sum should be 1(1-2^64)/(1-2). When you simplify it, it is actually equal to 2^64-1, not 2^64. You can't see that difference of 1 on your calculator. Try it on MSExcel. :)

Ralston Ros Mendoza - 7 years ago

Log in to reply

tested it , its 2^64 - 1.

at one point , i thought my mathematics has gone hay....

although i have to give an extra credit to 2048 game , finishing dat game only i suddenly remember back this question.

Ne-ko Nya - 6 years, 11 months ago

Hello,

as for 64 squares of having a=1 , r = 2,by geometric,

Sum of the 1st 64 terms = 1( 2^64 -1) / ( 2-1) ~ 1.84467 x 10^19 ,

By the 1st place, kingdom of the king = 1.5 x 10^15 = 1500 Trillions...

1.84467 x 10^9 > 1.5 x 10^15 by ~ 12 300 times....haha...sure the King became a beggar onwards...

The king should pay 3.689348815*10^19$ so he will bankrupt

Ahmed Rauf - 7 years ago

Log in to reply

3.689348815*10^19$

Ahmed Rauf - 7 years ago

the king had to pay 2 power 64 dollars. and went bankrupt

dilip Krishna - 7 years ago

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...