If 1+2+3+...+n=n (n+1), then 3 (1+3+5+....+69)=? Pick one.
A) 3675	B) 3575	C) 3475	D) 3375	E) 3275
Explanation :   To solve this use the formula of 3675P,   Sn= (n/2)(a+l) ................(1)   To find n, use   =&gt; Tn= a+(n-1)d   =&gt; 69=1+(n-1)2   =&gt; n=35   Use value of n in (1)   then,   Sn = (35/2)(1+69) = 1225   3675ns:- 3(Sn) = 3675   3675nswer : 3675
<result>A</result>
If 1+2+3+...+n=n (n+1), then 3 (1+3+5+....+69)=?