What is the sum of a 6-term geometric series if the first term is 22 and the last term is 369,754? Answers to choose from.

a)372,552
b)392,160
c)411,768
d)431,376

Question

What is the sum of a 6-term geometric series if the first term is 22 and the last term is 369,754? Answers to choose from.

a)372,552
b)392,160
c)411,768
d)431,376

anonymous · Answer

Term n = ar^n-1
This gives you the value of the nth term
Sub in n=6, a=22 and Tn = 359754

anonymous · Answer

Sum of nth term = (a(r^n -1))/(r-1)
Sub in values to find sum

anonymous · Answer

okay

anonymous · Answer

hey could you please plug the numbers in and ill multiply im a little confused @Skaematik

anonymous · Answer

@sauravshakya

anonymous · Answer

tn = a r^n-1
a = 22
n=6
Tn = 359754

anonymous · Answer

sn =  (a(r^n -1))/(r-1)

a = 22
n=6
sn= ?
r= find r from previous formula

anonymous · Answer

thats the problem im having is how to plug the numbers in @Skaematik

anonymous · Answer

trying plugging them

anonymous · Answer

i Have and the answer i got was 411,768 is that correct? @Skaematik

anonymous · Answer

You need to use the exact value of the r value. Do not round up or down.
I got 420094

anonymous · Answer

ohh i see thankyou very much

anonymous · Answer

@sauravshakya can you help me

anonymous · Answer

@bloodrain

anonymous · Answer

The answer you got was not any of the ones listed @Skaematik

anonymous · Answer

431376

anonymous · Answer

thank you

anonymous · Answer

$$369754 = 22 * r ^{6-1}$$$$S _{n}=\frac{ a \left( r ^{n}-1 \right) }{ r-1}$$

anonymous · Answer

thank you