Question

1supra100 + 2supra10 + ... + 99supra100=

Answer 1

$\displaystyle S=\frac{1}{100}+\frac{2}{100}+\frac{3}{100}+...+\frac{99}{100} \\ \\ S=\frac{1+2+3+4+...+99}{100} \\ \\ S'=1+2+3+4+...+99 \\ \\ S'=99+98+97+...+1 \\ \\ 2S'=100+100+100+...+100(99~termeni) \\ \\ S'=\frac{99\times 100}{2}=99\times 50=4950 \\ \\ S=\frac{4950}{100}=49,5$

Answer 2

1/100+2/100+..99/100=
=(1+2+..+99)/100
=99*100:2/100
=49.5