Sum 7+10+13+15+...+97+100 = ?

[dduclam]

Find the sum:

[Math Tutor]

Are you shure that the problem is not
P = 7 + 10 + 13 + 16 + ... + 97 + 100 ?

[dduclam]

Are you shure that the problem is not
P = 7 + 10 + 13 + 16 + ... + 97 + 100 ?

Yes,thank you,teacher P = 7 + 10 + 13 + 16 + ... + 97 + 100

[icb]

This is an arithmetical progression.

[prasanna_chandran]

1st term is 7, last term is 100, d- common difference is 3.

So we need only n, to find out the Sn=1/2 (a 1st term + a nth term) * n

=1/2*(7+100)*n

100=(7+31*3) , where a=7, 3=d, and a(nth) term = 100, and 31 is the (n-1)th term.

total terms= 32.

Sn= 1/2(7+100)*32= 16*107=1712.