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UKMT Intermediate Mathematical Challenge, 2023

Combinatorics Difficulty 2.0 Junior Find the answer United Kingdom

To draw a 3 by 3 square grid you need 8 straight lines, as shown. How many straight lines do you need to draw a $n$ by $n$ square grid?

(A) $n+5$ (B) $3n-1$ (C) $n^2-1$ (D) $4(n-1)$ (E) $2(n+1)$

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