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Olympiad workbook
Exam
Olympiad workbook
Subject
IOQM
Chapter
Permutation and Combination

Olympiad workbook · IOQM · Permutation and Combination

The six sides of a convex hexagon A_1 A_2 A_3 A_4 A_5 A_6 are...

The six sides of a convex hexagon A1A2A3A4A5A6A_1 A_2 A_3 A_4 A_5 A_6 are colored red. Each of the diagonals of the hexagon is colored either red or blue. If NN is the number of colorings such that every triangle AiAjAkA_i A_j A_k, where 1≤l<j<k≤61 \leq l < j < k \leq 6, has at least one red side, find the sum of the squares of the digits of NN.The six sides of a convex hexagon A_1 A_2 A_3 A_4 A_5 A_6 are colored red. Each of the diagonals of the hexagon is

Correct answer

94

Step-by-step solution

The six sides of a convex hexagon A_1 A_2 A_3 A_4 A_5 A_6 are colored red. Each of the diagonals of the hexagon is
Number of ways such that atleast one side of △A2A4A6 is red =3C1×22−3C2×2+3C320=7\begin{aligned} \triangle A_2 A_4 A_6 \text { is red } & ={ }^3 C_1 \times 2^2-{ }^3 C_2 \times 2+{ }^3 C_3 2^0 \\ & =7 \end{aligned} Number of ways such that atleast one side of △A1A3A5\triangle A_1 A_3 A_5 is red =7=7 Number of ways to colour diagonals A1A4,A2A5A_1 A_4, A_2 A_5, \begin{aligned} & A_3 A_6=2^3=8 \\ & \begin{aligned} \therefore \text { Required number } & =8 \times 7 \times 7 \\ & =392=\mathrm{N} \\ \therefore \text { Sum of square of digits } & =3^2+9^2+2^2 \\ & =94 \end{aligned} \end{aligned}$
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