maihuna wrote:If S1, S2, S3, ... , S50 are the sums of 20 terms of AP series whose first terms are 1, 2, 3, 4, ..., and whose common difference are 1,3,5,7,...what is the value of:

S1+S2+S3+..+S50

S1, first term = 1, common difference = 1, no. of terms = 20

S2, first term = 2, common difference = 2, no. of terms = 20

so on and so forth.

sum of S1 = 20/2 [ 2*1 + (19)1]
sum of S2 = 20/2 [ 2*2 + (19)2]
sum of S3 = 20/2 [ 2*3 + (19)3]

so on and so forth

now you can easily identify the pattern

10[2+19] * [1+2+3+4+5.....+50]

10*21*1275 = 210*1275

is it 487750??

is it 500500