Question

Aratati ca 1/6+1/7+1/8+1/9...+1/30<5

Answer 1

(1/6+1/7+1/8+..............+1/30)<5

de la 1/6 pana la 1/30 sunt 30-6+1=25 de fractii

1/6+1/7+1/8+..............+1/30< 1/6+1/6+1/6+….+1/6; (de 25 de ori 1/6)

1/6+1/7+1/8+..............+1/30<25/6=125/30<150/30=5

=> 1/6+1/7+1/8+..............+1/30<5 (A)