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3 years ago

What is the sum of the first five terms of a geometric series with a1=15 and r=1/3

Mathematics

2 answers:

Solnce55 [7]3 years ago

6 0

Answer:

15, 5, 5/3, 5/9, 5/27

Step-by-step explanation:

Recall, that the general form of a geometric series is

a, ar, ar², ar³, .........

where a is the first term and r is the ratio

It is given that the first time is 15, hence a = 15

also given that ratio is 1/3

hence the first 5 terms are:

15, (15)(1/3), (15)(1/3)^2, (15)(1/3)^3, (15)(1/3)^4

simplifying each term gives

15, 5, 5/3, 5/9, 5/27

Talja [164]3 years ago

3 0

Answer:

605/27 or 22.41 to the nearest hundredth.

Step-by-step explanation:

The formula for the sum of n terms is

an = a1 * (1 - r^n) / (1 - r) where a1 = the first term and r = the common difference.

So here a5 = 15 * (1 - (1/3)^5) / (1 - 1/3)

= 605/27

= 22.41 to the nearest hundredth.

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What conclusions can be made about the amount of money in each account if f represents Molly's account and g represents her brot

Nat2105 [25]

Answer:

(b) is true

Step-by-step explanation:

Given

Molly

$a = 500$ --- starting balance

$m = 10$ --- monthly rate

Her brother

$a = 100$ ---- starting balance

$r = 10\%$ --- annual rate

Required

Determine which option is true

First, we calculate her brother's function.

The function is an exponential function calculated as:

$y = ab^x$

Where $b = 1 + r$

So, we have:

$y = ab^x$

$y = 100 *(1 + 10\%) ^x$

$y = 100 *(1 + 0.10) ^x$

$y = 100 *(1.10) ^x$

Hence:

$g(x) = 100 *(1.10) ^x$

Next, we calculate Molly's function (a linear function)

The monthly function is:

$y = mx + a$

So, we have:

$y = 10x + 500$

Annually, the function will be:

$y = 10x*12 + 500$

$y = 120x + 500$

So, we have:

$f(x) = 120x + 500$

At this point, we have:

$f(x) = 120x + 500$ ---- Molly

$g(x) = 100 *(1.10) ^x$ ---- Her brother

<u>Next, we test each option</u>

(a): Molly's account will have a faster rate of change over [32,40]

We calculated Molly's function to be:

$y = 120x + 500$

The slope of a linear function with the form: $y = mx + b$ is m

By comparison:

$m = 120$

Since Molly's account is a linear function, the rate of change over any interval will always be the same; i.e.

$m = 120$

For his brother:

Rate of change is calculated using:

$m = \frac{g(b) - g(a)}{b - a}$

$m = \frac{g(40) - g(32)}{40 - 32}$

$m = \frac{g(40) - g(32)}{8}$

Calculate g(40) and g(32)

$g(x) = 100 *(1.10) ^x$

$g(40) = 100 * 1.10^{40} =4526$

$g(32) = 100 * 1.10^{32} = 2111$

So, we have:

$m = \frac{4526 - 2111}{8}$

$m = \frac{2415}{8}$

$m = 302$

By comparison: $302 > 120$

Hence, her brother's account has a faster rate over [32,40]

(a) is false

(b): Molly's account will have a slower rate of change over [24,30]

$m = 120$ --- Molly's rate of change

For his brother:

$m = \frac{g(b) - g(a)}{b - a}$

$m = \frac{g(30) - g(24)}{30 - 24}$

$m = \frac{g(30) - g(24)}{6}$

Calculate g(30) and g(24)

$g(x) = 100 *(1.10) ^x$

$g(40) = 100 * 1.10^{30} =1745$

$g(32) = 100 * 1.10^{24} = 985$

So, we have:

$m = \frac{g(30) - g(24)}{6}$

$m = \frac{1745 - 985}{6}$

$m = \frac{760}{6}$

$m = 127$

By comparison: $127 > 120$

Hence, Molly's account has a slower rate over [24,30]

(b) is false

(c): Molly's account will have a slower rate of change over [0,4]

$m = 120$ --- Molly's rate of change

For his brother:

$m = \frac{g(b) - g(a)}{b - a}$

$m = \frac{g(4) - g(0)}{4 - 0}$

$m = \frac{g(4) - g(0)}{4}$

Calculate g(4) and g(0)

$g(x) = 100 *(1.10) ^x$

$g(4) = 100 * 1.10^4 =146$

$g(0) = 100 * 1.10^{0} = 100$

So, we have:

$m = \frac{g(4) - g(0)}{4}$

$m = \frac{146 - 100}{4}$

$m = \frac{46}{4}$

$m = 11.5$

By comparison: $120>11.5$

Hence, Molly's account has a faster rate over [0,4]

(c) is false

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3 years ago

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ki77a [65]

R = (2s - 6t + 5)/2
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3 years ago

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Westkost [7]

Answer:

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3 years ago

X = 3y - 6 2x - 4y = 8 Solve the system of equations using substitution.

Brut [27]

Hello

x = 3y - 6
2x - 4y = 8
We need to start by solving 3y - 6 for x
Substitute 3y -6 for x in 2x
2x - 4y = 8
2(3y - 6) - 4y = 8
2y - 12 = 8
2y = 8 + 12
2y = 20
Divide both sides by 2
2y/2 = 20/2
y = 10

Now, substitute 10 for y in x= 3y
x = 3y - 6
x = 3(10) - 6
x = 30 - 6
x= 24

Answer : x = 24 and y=10

I hope this help!

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