Maze Of Matrices

Algebra Level 4

( 1 1 1 1 1 1 2 3 4 5 1 3 6 10 15 1 4 10 20 35 1 5 15 35 70 ) ( 2 2 2 2 2 2 4 6 8 10 2 6 12 20 30 2 8 20 40 70 2 10 30 70 140 ) = ( a b c d e b f g h i c g j k l d h k m n e i l n o ) \begin{pmatrix} 1 & 1 & 1 & 1 & 1 \\ 1 & 2 & 3 & 4 & 5 \\ 1 & 3 & 6 & 10 & 15 \\ 1 & 4 & 10 & 20 & 35 \\ 1 & 5 & 15 & 35 & 70 \end{pmatrix}\begin{pmatrix} 2 & 2 & 2 & 2 & 2 \\ 2 & 4 & 6 & 8 & 10 \\ 2 & 6 & 12 & 20 & 30 \\ 2 & 8 & 20 & 40 & 70 \\ 2 & 10 & 30 & 70 & 140 \end{pmatrix}=\begin{pmatrix} a & b & c & d & e \\ b & f & g & h & i \\ c & g & j & k & l \\ d & h & k & m & n \\ e & i & l & n & o \end{pmatrix}

Find a + f + j + m + o a+f+j+m+o .


The answer is 17098.

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1 solution

Tom Engelsman
Nov 25, 2017

Upon observation, the second matrix is twice the first (call the first 5x5 symmetric matrix A A ). We simply need to calculate t r a c e ( 2 A 2 ) , trace(2A^{2}), which is done by focusing on just the i t h i-th row & column ( i = 1 , 2 , 3 , 4 , 5 i = 1,2,3,4,5 ):

a = 2 ( 1 2 + 1 2 + 1 2 + 1 2 + 1 2 ) = 10 ; a = 2(1^2 + 1^2 + 1^2 + 1^2 + 1^2) = 10;

f = 2 ( 1 2 + 2 2 + 3 2 + 4 2 + 5 2 ) = 110 ; f = 2(1^2 + 2^2 + 3^2 + 4^2 + 5^2) = 110;

j = 2 ( 1 2 + 3 2 + 6 2 + 1 0 2 + 1 5 2 ) = 742 ; j = 2(1^2 + 3^2 + 6^2 + 10^2 + 15^2) = 742;

m = 2 ( 1 2 + 4 2 + 1 0 2 + 2 0 2 + 3 5 2 ) = 3484 ; m = 2(1^2 + 4^2 + 10^2 + 20^2 + 35^2) = 3484;

o = 2 ( 1 2 + 5 2 + 1 5 2 + 3 5 2 + 7 0 2 = 12752. o = 2(1^2 + 5^2 + 15^2 + 35^2 + 70^2 = 12752.

and a + f + j + m + o = 17 , 098 . a + f + j + m + o = \boxed{17,098}.

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