Question

1/3<1/31+1/32+...+1/40<1/4

Answer 1

1/3=10/30=1/30+1/30+1/30…..+1/30 (de 10 ori)

1/4=10/40=1/40+1/40+…..+1/40  (de 10 ori)

1/30+1/30+…..+1/30>1/31+1/32+1/33+….+1/40>1/40+1/40+….+1/40

10/30>1/31+1/32+1/33+….+1/40>10/40

deci, 1/3>1/31+1/32+1/33+….+1/40>1/4

Obs. de la 31 la 40 sunt 10 nr