All categories

3 years ago

The sum of an infinite geometric series is three times the first term. Find the common ratio of this series.

Mathematics

1 answer:

adelina 88 [10]3 years ago

3 0

Answer:

$\frac{2}{3}$

Step-by-step explanation:

The sum of an infinite geometric series is expressed according to the formula;

$S_\infty = \dfrac{a}{1-r}$ where;

a is the first term of the series

r is the common ratio

If the sum of an infinite geometric series is three times the first term, this is expressed as $S_\infty = 3a$

Substitute $S_\infty = 3a$ into the formula above to get the common ratio r;

$3a = \dfrac{a}{1-r} \\\\$

$cross \ multiply\\\\3a(1-r) = a\\\\3(1-r) = 1\\$

open the parenthesis

$3 - 3r = 1\\\\$

subtract 3 from both sides

$3 - 3r -3= 1-3\\\\-3r = -2\\\\r = \frac{2}{3}$

Hence the common ratio of this series is $\frac{2}{3}$

You might be interested in

A cab charges $1.45 for a flat fee and $0.55 for each mile. write and solve an inequality to determine how many miles Ariel can

BigorU [14]

35-1.45=33.55
33.55/0.55=62
61 Miles

7 0

3 years ago

The U.S. Census Bureau conducts a study to determine the time needed to complete the short form. The Bureau surveys 200 people.

NISA [10]

Answer:

$8.2-2.58\frac{2.2}{\sqrt{18}}=6.86$

$8.2+2.58\frac{2.2}{\sqrt{18}}=9.54$

So on this case the 90% confidence interval would be given by (6.86;9.54) And the error is given by:

$ME= 2.58\frac{2.2}{\sqrt{18}} =1.338$

Step-by-step explanation:

Previous concepts

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".

The margin of error is the range of values below and above the sample statistic in a confidence interval.

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

$\bar X=8.2$ represent the sample mean for the sample

$\mu$ population mean (variable of interest)

$\sigma=2.2$ represent the population standard deviation

n represent the sample size

Solution to the problem

The confidence interval for the mean is given by the following formula:

$\bar X \pm z_{\alpha/2}\frac{\sigma}{\sqrt{n}}$ (1)

Since the Confidence is 0.90 or 90%, the value of $\alpha=0.1$ and $\alpha/2 =0.005$ , and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-NORM.INV(0.005,0,1)".And we see that $z_{\alpha/2}=2.58$