Question

Find the sum of the first 7 terms of the following sequence. Round to the nearesthundredth if necessary.

Answer 1

Given the sequence:

$50,61,74.42,\ldots$

The given sequence has a common ratio = r

$r=\frac{61}{50}=\frac{74.42}{61}=1.22$

we will find the sum of the first 7 terms as follows:

$\begin{gathered} S_n=\frac{a_1-a_1\cdot r^n}{1-r} \\ \\ a_1=50 \\ r=1.22 \\ n=7 \end{gathered}$

Substitute with a1, r, and n into the formula Sn

so,

$S_7=\frac{50-50\cdot(1.22)^7}{1-1.22}=686.9797$

Round to the nearest hundredth

So, the answer will be sum = 686.98