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## Answers

=n(n+1) =50*51 =2550

sum of integers from 1 to 100 that are divisible by 5 but not divisible by 2. are 5,15,.25,----------95

= 10/2 (5+95) = 500

The sum of integers from 1 to 100 that are divisible by 2 or 5 is=2550+500=3050 is the answer

by using formula An = A + (n-1)d

here An = 100 , A = 2

n = 50

then by using formula Sn = n/2 (2a + (n-1)d)

by putting values Sn = 2500

the series formed divi by 5 : 5, 10, 15 .... 100

here n = 20

and Sn = 1050