3) 100, 50, 25, .....

\(\displaystyle{r}={\frac{{{50}}}{{{100}}}}={\frac{{{1}}}{{{2}}}}\)

Sum of GP \(\displaystyle={a}{\left({\frac{{{1}−{r}^{{{n}}}}}{{{1}−{r}}}}\right)}\)

\(\displaystyle={100}{\left({\frac{{{1}−{0.5}^{{{5}}}}}{{{1}−{0.5}}}}\right)}\)

\(\displaystyle={193.75}\)

Now, follow same process for the other sequences.

\(\displaystyle{r}={\frac{{{50}}}{{{100}}}}={\frac{{{1}}}{{{2}}}}\)

Sum of GP \(\displaystyle={a}{\left({\frac{{{1}−{r}^{{{n}}}}}{{{1}−{r}}}}\right)}\)

\(\displaystyle={100}{\left({\frac{{{1}−{0.5}^{{{5}}}}}{{{1}−{0.5}}}}\right)}\)

\(\displaystyle={193.75}\)

Now, follow same process for the other sequences.