Question

Scrieți sub forma zecimală fracția 7+14+21+...+210 supra 30

Answer 1

[tex] \frac{7+14+21+...+210}{30}=\\ \\= \frac{7+7*2+7*3+...+7*30}{30}=\\ \\= \frac{7*(1+2+3+...+30)}{30}=\\ \\= \frac{7* \frac{30*31}{2} }{30}=\\ \\= \frac{7*15*31 }{30}=\\ \\= \frac{7*31 }{2}=\\ \\=108.5[/tex]