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2013 CEMC Gauss (Grade 7) Problems/Problem 4

The value of 1 + 1 − 2 + 3 + 5 − 8 + 13 + 21 − 34 is

$\textbf{(A)}\ -32 \qquad\textbf{(B)}\ 1\qquad\textbf{(C)}\ 88\qquad\textbf{(D)}\ 0\qquad\textbf{(E)}\ -34$

Solution

We can group it by three to give (1+1-2)+(3+5-8)+(13+21-34) which simplifies to (0)+(0)+(0)=$\boxed{\textbf{(D)}\ 0}$

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