Question

Calculati suma:
S=1+4+7+10+....+40+43+46=
Stiind ca suma are 16 termeni.
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Answer 1

S=1+46+4+43+7+40+...=47+47+47...+47=8*47=376

Answer 2

$\displaystyle S_1_6= \frac{2+ 15 \times 3}{2} \times 16 \\ \\ S_1_6= \frac{2+45}{2} \times 16 \\ \\ S_1_6= \frac{47}{2} \times 16 \\ \\ S_1_6=47 \times 8 \\ \\ S_1_6=376$