Rolling a die 1000 times , a string of the product will be a cube
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Each of the six faces of a die is marked with an integer, not necessarily positive. The
die is rolled 1000 times. Show that there is a time interval such that the product of all rolls
in this interval is a cube of an integer. (For example, it could happen that the product of
all outcomes between 5th and 20th throws is a cube; obviously, the interval has to include
at least one throw!)
i looked at abcdef as a possible product , somehow 1000 of these 'terms' no matter how we shuffle them , a product like ababab or adadad or acdacdacd will be in the string but i cant prove how :(
combinatorics
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add a comment |
$begingroup$
Each of the six faces of a die is marked with an integer, not necessarily positive. The
die is rolled 1000 times. Show that there is a time interval such that the product of all rolls
in this interval is a cube of an integer. (For example, it could happen that the product of
all outcomes between 5th and 20th throws is a cube; obviously, the interval has to include
at least one throw!)
i looked at abcdef as a possible product , somehow 1000 of these 'terms' no matter how we shuffle them , a product like ababab or adadad or acdacdacd will be in the string but i cant prove how :(
combinatorics
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add a comment |
$begingroup$
Each of the six faces of a die is marked with an integer, not necessarily positive. The
die is rolled 1000 times. Show that there is a time interval such that the product of all rolls
in this interval is a cube of an integer. (For example, it could happen that the product of
all outcomes between 5th and 20th throws is a cube; obviously, the interval has to include
at least one throw!)
i looked at abcdef as a possible product , somehow 1000 of these 'terms' no matter how we shuffle them , a product like ababab or adadad or acdacdacd will be in the string but i cant prove how :(
combinatorics
$endgroup$
Each of the six faces of a die is marked with an integer, not necessarily positive. The
die is rolled 1000 times. Show that there is a time interval such that the product of all rolls
in this interval is a cube of an integer. (For example, it could happen that the product of
all outcomes between 5th and 20th throws is a cube; obviously, the interval has to include
at least one throw!)
i looked at abcdef as a possible product , somehow 1000 of these 'terms' no matter how we shuffle them , a product like ababab or adadad or acdacdacd will be in the string but i cant prove how :(
combinatorics
combinatorics
asked 3 hours ago
Randin DRandin D
826
826
add a comment |
add a comment |
1 Answer
1
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We can show something stronger; there exists an interval of rolls where each side has appeared a number of times which is a multiple of $3$.
For each $i=1,2,dots,1000$, let $a_i$ be number of times that the first face has appeared in rolls numbered $1,2,dots,i$. Same for $b_i,c_i,d_i,e_i,f_i$. Consider the $1000$ ordered six-tuples of values $T_i:=(a_i,b_i,dots,f_i)$, where each coordinate is only recorded modulo $3$. There are $3^6=729$ possible six-tuples, and there are $1000$ rolls, so by the pigeonhole principle, there are two indices $i<j$ for which $T_i=T_j$. This implies that among rolls numbered $i+1,i+2,dots,j$, each face appears a number of times which is a multiple of three.
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i dont get it, how again can u use pigeonhole? and how does this work for cubes not 3k
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– Randin D
2 hours ago
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(a) There are $1000$ numbers $iin{1,2,dots,1000}$, and $729$ possible tuples. $1000$ pigeons in $729$ holes. (b) If each face appears a multiple of three times, and the numbers of the faces are $x,y,z,w,s,t$, then the product of the numbers in that interval $[i+1,j]$ is $x^{3i}y^{3j}cdots t^{3k}$, which is the cube of $x^iy^jcdots t^k$.
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– Mike Earnest
2 hours ago
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i get pigeonhole ..1000 into 729 means 3 will be in one pigeonhole right? and thats the cube?
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– Randin D
2 hours ago
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how do u get the 729 again?
$endgroup$
– Randin D
2 hours ago
add a comment |
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1 Answer
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1 Answer
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active
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active
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$begingroup$
We can show something stronger; there exists an interval of rolls where each side has appeared a number of times which is a multiple of $3$.
For each $i=1,2,dots,1000$, let $a_i$ be number of times that the first face has appeared in rolls numbered $1,2,dots,i$. Same for $b_i,c_i,d_i,e_i,f_i$. Consider the $1000$ ordered six-tuples of values $T_i:=(a_i,b_i,dots,f_i)$, where each coordinate is only recorded modulo $3$. There are $3^6=729$ possible six-tuples, and there are $1000$ rolls, so by the pigeonhole principle, there are two indices $i<j$ for which $T_i=T_j$. This implies that among rolls numbered $i+1,i+2,dots,j$, each face appears a number of times which is a multiple of three.
$endgroup$
$begingroup$
i dont get it, how again can u use pigeonhole? and how does this work for cubes not 3k
$endgroup$
– Randin D
2 hours ago
$begingroup$
(a) There are $1000$ numbers $iin{1,2,dots,1000}$, and $729$ possible tuples. $1000$ pigeons in $729$ holes. (b) If each face appears a multiple of three times, and the numbers of the faces are $x,y,z,w,s,t$, then the product of the numbers in that interval $[i+1,j]$ is $x^{3i}y^{3j}cdots t^{3k}$, which is the cube of $x^iy^jcdots t^k$.
$endgroup$
– Mike Earnest
2 hours ago
$begingroup$
i get pigeonhole ..1000 into 729 means 3 will be in one pigeonhole right? and thats the cube?
$endgroup$
– Randin D
2 hours ago
$begingroup$
how do u get the 729 again?
$endgroup$
– Randin D
2 hours ago
add a comment |
$begingroup$
We can show something stronger; there exists an interval of rolls where each side has appeared a number of times which is a multiple of $3$.
For each $i=1,2,dots,1000$, let $a_i$ be number of times that the first face has appeared in rolls numbered $1,2,dots,i$. Same for $b_i,c_i,d_i,e_i,f_i$. Consider the $1000$ ordered six-tuples of values $T_i:=(a_i,b_i,dots,f_i)$, where each coordinate is only recorded modulo $3$. There are $3^6=729$ possible six-tuples, and there are $1000$ rolls, so by the pigeonhole principle, there are two indices $i<j$ for which $T_i=T_j$. This implies that among rolls numbered $i+1,i+2,dots,j$, each face appears a number of times which is a multiple of three.
$endgroup$
$begingroup$
i dont get it, how again can u use pigeonhole? and how does this work for cubes not 3k
$endgroup$
– Randin D
2 hours ago
$begingroup$
(a) There are $1000$ numbers $iin{1,2,dots,1000}$, and $729$ possible tuples. $1000$ pigeons in $729$ holes. (b) If each face appears a multiple of three times, and the numbers of the faces are $x,y,z,w,s,t$, then the product of the numbers in that interval $[i+1,j]$ is $x^{3i}y^{3j}cdots t^{3k}$, which is the cube of $x^iy^jcdots t^k$.
$endgroup$
– Mike Earnest
2 hours ago
$begingroup$
i get pigeonhole ..1000 into 729 means 3 will be in one pigeonhole right? and thats the cube?
$endgroup$
– Randin D
2 hours ago
$begingroup$
how do u get the 729 again?
$endgroup$
– Randin D
2 hours ago
add a comment |
$begingroup$
We can show something stronger; there exists an interval of rolls where each side has appeared a number of times which is a multiple of $3$.
For each $i=1,2,dots,1000$, let $a_i$ be number of times that the first face has appeared in rolls numbered $1,2,dots,i$. Same for $b_i,c_i,d_i,e_i,f_i$. Consider the $1000$ ordered six-tuples of values $T_i:=(a_i,b_i,dots,f_i)$, where each coordinate is only recorded modulo $3$. There are $3^6=729$ possible six-tuples, and there are $1000$ rolls, so by the pigeonhole principle, there are two indices $i<j$ for which $T_i=T_j$. This implies that among rolls numbered $i+1,i+2,dots,j$, each face appears a number of times which is a multiple of three.
$endgroup$
We can show something stronger; there exists an interval of rolls where each side has appeared a number of times which is a multiple of $3$.
For each $i=1,2,dots,1000$, let $a_i$ be number of times that the first face has appeared in rolls numbered $1,2,dots,i$. Same for $b_i,c_i,d_i,e_i,f_i$. Consider the $1000$ ordered six-tuples of values $T_i:=(a_i,b_i,dots,f_i)$, where each coordinate is only recorded modulo $3$. There are $3^6=729$ possible six-tuples, and there are $1000$ rolls, so by the pigeonhole principle, there are two indices $i<j$ for which $T_i=T_j$. This implies that among rolls numbered $i+1,i+2,dots,j$, each face appears a number of times which is a multiple of three.
answered 3 hours ago
Mike EarnestMike Earnest
28.5k22153
28.5k22153
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i dont get it, how again can u use pigeonhole? and how does this work for cubes not 3k
$endgroup$
– Randin D
2 hours ago
$begingroup$
(a) There are $1000$ numbers $iin{1,2,dots,1000}$, and $729$ possible tuples. $1000$ pigeons in $729$ holes. (b) If each face appears a multiple of three times, and the numbers of the faces are $x,y,z,w,s,t$, then the product of the numbers in that interval $[i+1,j]$ is $x^{3i}y^{3j}cdots t^{3k}$, which is the cube of $x^iy^jcdots t^k$.
$endgroup$
– Mike Earnest
2 hours ago
$begingroup$
i get pigeonhole ..1000 into 729 means 3 will be in one pigeonhole right? and thats the cube?
$endgroup$
– Randin D
2 hours ago
$begingroup$
how do u get the 729 again?
$endgroup$
– Randin D
2 hours ago
add a comment |
$begingroup$
i dont get it, how again can u use pigeonhole? and how does this work for cubes not 3k
$endgroup$
– Randin D
2 hours ago
$begingroup$
(a) There are $1000$ numbers $iin{1,2,dots,1000}$, and $729$ possible tuples. $1000$ pigeons in $729$ holes. (b) If each face appears a multiple of three times, and the numbers of the faces are $x,y,z,w,s,t$, then the product of the numbers in that interval $[i+1,j]$ is $x^{3i}y^{3j}cdots t^{3k}$, which is the cube of $x^iy^jcdots t^k$.
$endgroup$
– Mike Earnest
2 hours ago
$begingroup$
i get pigeonhole ..1000 into 729 means 3 will be in one pigeonhole right? and thats the cube?
$endgroup$
– Randin D
2 hours ago
$begingroup$
how do u get the 729 again?
$endgroup$
– Randin D
2 hours ago
$begingroup$
i dont get it, how again can u use pigeonhole? and how does this work for cubes not 3k
$endgroup$
– Randin D
2 hours ago
$begingroup$
i dont get it, how again can u use pigeonhole? and how does this work for cubes not 3k
$endgroup$
– Randin D
2 hours ago
$begingroup$
(a) There are $1000$ numbers $iin{1,2,dots,1000}$, and $729$ possible tuples. $1000$ pigeons in $729$ holes. (b) If each face appears a multiple of three times, and the numbers of the faces are $x,y,z,w,s,t$, then the product of the numbers in that interval $[i+1,j]$ is $x^{3i}y^{3j}cdots t^{3k}$, which is the cube of $x^iy^jcdots t^k$.
$endgroup$
– Mike Earnest
2 hours ago
$begingroup$
(a) There are $1000$ numbers $iin{1,2,dots,1000}$, and $729$ possible tuples. $1000$ pigeons in $729$ holes. (b) If each face appears a multiple of three times, and the numbers of the faces are $x,y,z,w,s,t$, then the product of the numbers in that interval $[i+1,j]$ is $x^{3i}y^{3j}cdots t^{3k}$, which is the cube of $x^iy^jcdots t^k$.
$endgroup$
– Mike Earnest
2 hours ago
$begingroup$
i get pigeonhole ..1000 into 729 means 3 will be in one pigeonhole right? and thats the cube?
$endgroup$
– Randin D
2 hours ago
$begingroup$
i get pigeonhole ..1000 into 729 means 3 will be in one pigeonhole right? and thats the cube?
$endgroup$
– Randin D
2 hours ago
$begingroup$
how do u get the 729 again?
$endgroup$
– Randin D
2 hours ago
$begingroup$
how do u get the 729 again?
$endgroup$
– Randin D
2 hours ago
add a comment |
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