In this case, we'll have to carry out several steps to find the solution.
Step 01:
Data:
![\sum_{n\mathop{=}1}^(20)4((8)/(9))\placeholder{⬚}^(n-1)](https://img.qammunity.org/2023/formulas/mathematics/college/jk3ssgb05kam7m92yw380xl8j5ydej6rkx.png)
Step 02:
summa
We must evaluate each term and perform the total sum.
n = 1:
![4\text{ \lparen}(8)/(9))\placeholder{⬚}^(1-1)=4((8)/(9))\text{ }^0=4\text{ * 1 = 4 }](https://img.qammunity.org/2023/formulas/mathematics/college/x2tbe15cr49ruc73qsrqbdhwqt5mwtkdxr.png)
n = 2:
![4\text{ \lparen}(8)/(9))\placeholder{⬚}^(2-1)=4((8)/(9))\placeholder{⬚}^1=\text{ 4 * \lparen}(8)/(9))=(32)/(9)](https://img.qammunity.org/2023/formulas/mathematics/college/b6poey3cbmnd23vzfwrwqf78mui9a2r7f9.png)
The following terms (from 3 to 20) can be evaluated in the same way as above.
total sum:
![\sum_{n\mathop{=}1}^24((8)/(9))\placeholder{⬚}^(n-1)=32.59](https://img.qammunity.org/2023/formulas/mathematics/college/ujwn6i1g3n231pnkljsmo2e3btmh8d833b.png)
The answer is:
32.59