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Sum of no between 50 and 500 dividisible by 7

Answer» first no div by 7 = 56 = a1last no div by 7 = 497=aL497=56+(n-1)7497-49=7nn=448/7=64S64=64/2(2a+63d) = 32 x (112+441) = 32 x 553 = 17696


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