Question

Find the sum of the geometric sequence. three divided by two, three divided by eight, three divided by thirty two, three divided by one hundred and twenty eight, three divided by five hundred and twelve

Answer 1

Answer: we have that

[3/2,3/8,3/32,3/128,3/512]

the sum of the geometric sequence is [3/2+3/8+3/32+3/128+3/512]

=(1/512)*[256*3+64*3+16*3+4*3]

=(3/512)*[256+64+16+4]

=(3/512)*[340]

=(1020/512)

=255/128---------> 1.9922

the answer is

1.9922

another way to calculate it

is through the following formula

∑=ao*[(1-r^n)/(1-r)]

where

ao---------> is the first term

r----------> is the common ratio between terms

n----------> is the number of terms

ao=1.5

r=1/4-----> 0.25

n=5

so

∑=1.5*[(1-0.25^5)/(1-0.25)]-------------> 1.99

Step-by-step explanation: we have that

[3/2,3/8,3/32,3/128,3/512]

the sum of the geometric sequence is [3/2+3/8+3/32+3/128+3/512]

=(1/512)*[256*3+64*3+16*3+4*3]

=(3/512)*[256+64+16+4]

=(3/512)*[340]

=(1020/512)

=255/128---------> 1.9922

the answer is

1.9922

another way to calculate it

is through the following formula

∑=ao*[(1-r^n)/(1-r)]

where

ao---------> is the first term

r----------> is the common ratio between terms

n----------> is the number of terms

ao=1.5

r=1/4-----> 0.25

n=5

so

∑=1.5*[(1-0.25^5)/(1-0.25)]-------------> 1.99