Question

s= 4+7+10+13+.....+334

Answer 1

4 = 3·1 +  1

7 = 3·2 +  1

10 = 3·3 + 1
.
.
.
334 = 3·111 + 1
______________

S = 3·(1+2+3+ ... +111) +111 = 3·111·112/2+111= 3·111·56 +111 =

=111(3·56 +1) = 111·169 =18 759