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What is the sum of 2 digit multiples of 11?

User CSteusloff
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1 Answer

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M_(11)=\{11;22;33;44;55;66;77;88;99 \} \\\\ S=11+22+33+....+99 \\\\ S=((11+99)*9)/(2) \\\\ S=(110*9)/(2) \\\\ S=55*9 \\\\ \boxed{S=495}
User DukeSilver
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