Question

S=2+4+6+8+........+476;

Answer 1

s=2(1+2+3+4+.....+238)
s=2 × 238 × 239 ÷ 2
s= 238×239
s=56882

Answer 2

1+2+....476=
476x477:2=113526

1+2..+476=
2+4+6+....476+ 1+3+5....+475
2+4+...476=113526:2=56763

sau 
sunt 238 numere
238x477:2-56763