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11+22+33+....+198 calculeaza suma

Răspuns :

S=3*[(198+11)*3)
S=3*(209*3)
S=3*627
S=1881
11+22+33+....+198 =
dam factor comun pe 11
= 11 × (1 + 2 + 3 +...+ 18) =

= 11 × 18 × (18 + 1) : 2 =

= 11 × 9 × 19 =

= 99 × 19 =

= 1 881