Question

Find the sum of all three digit numbers which leaves remainder 1 on

division by 7? പ്ലസ് say​

Answer 1

ANSWER

3 digit  numbers = 100  , 101 ..... 999

   3 digit numbers  which divided by 4 leaves 1 as remainder are   101, 105, 109,  ....................997

  the total  number of terms = = Tn =  101 +  { n-1} 4 == 997

                           101 +4n - 4 = 997

                           97 +4n == 997

                                4n = 900

                       ===> 900 / 4 = 225

  the sum of  225 terms = Sn = 225/ 2  { 2 (101) +( 225-1) 4

             225 [ / 2 [  202+896] ==> 123525

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