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r-ruslan [8.4K]

3 years ago

6

cell Phone plan A costs $70 per month and comes with a free $500 phone, cell phone B costs $50 per mouth but does not come with

a phone. If you buy the $500 phone an choose plan , how many mouths is it until your cost is the same as plan A’s?

1 answer:

Levart [38]3 years ago

7 0

Answer:

It will be 25 months

Step-by-step explanation:

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The circumference of a sphere was measured to be 80 cm with a possible error of 0.5 cm. A) Use differentials to estimate the max

siniylev [52]

Answer:

A) The maximum error in the calculated surface area: $25cm^2$

Relative error: $0.013$

B) The maximum error in the calculated volume: $162cm^2$

Relative error: $0.019$

Step-by-step explanation:

A) The formula for the surface area is:

$A=4\pi r^2$

The measured value is the circumference which is equal to:

$C=2\pi r$

then the radius is:

$r=\frac{C}{2\pi}$

Substituting in the formula of the surface:

$A=4\pi(\frac{C}{2\pi})^2\\A=4\pi(\frac{C^2}{4\pi^2})\\A=\frac{C^2}{\pi}$

Using the formula to calculate the error:

$dy=f'(x)dx$

Where $x$ is the variable measured and $y$ is a function of $x$ ( $y=f(x)$ ).

$dA=f'(C)dC\\dA=\frac{2C^{(2-1)}}{\pi}dC\\dA=\frac{2C}{\pi}dC$

We have C=80cm and dC=0.5cm

$dA=\frac{2C}{\pi}dC\\dA=\frac{2(80)}{\pi}(0.5)\\dA=\frac{160}{\pi}(0.5)\\dA=50.9296(0.5)\\dA=25.4648\approx25cm^2$

The relative error is the maximum error divide by the total area. The total area is: $A=\frac{C^2}{\pi}=\frac{(80)^2}{\pi}=\frac{6400}{\pi}=2037.1833cm^2$

$\frac{dA}{A}=\frac{25.4648}{2037.1833} =0.0125\approx0.013$

B) The formula for the volume is:

$V=\frac{4}{3} \pi r^3$

Using $r=\frac{C}{2\pi}$

$V=\frac{4}{3} \pi r^3\\V=\frac{4}{3} \pi (\frac{C}{2\pi})^3\\V=\frac{4}{3} \pi (\frac{C^3}{8\pi^3})\\V=\frac{1}{3}(\frac{C^3}{2\pi^2})\\V=\frac{C^3}{6\pi^2}$

The maximum error is:

$dV=\frac{3C^{3-1}}{6\pi^2}dC\\dV=\frac{C^{2}}{2\pi^2}dC\\dV=\frac{(80)^{2}}{2\pi^2}(0.5)\\dV=\frac{6400}{2\pi^2}(0.5)\\dV=\frac{6400}{2\pi^2}(0.5)\\dV=(324.2278)(0.5)\\dV=162.1139\approx162cm^2$

The calculated volume is:

$V=\frac{C^3}{6\pi^2}\\V=\frac{(80)^3}{6\pi^2}\\V=\frac{512000}{6\pi^2}\\V=8646.0743$

The relative error is:

$\frac{dV}{V}=\frac{162.1139}{8646.0743}=0.0188\approx0.019$

3 0

2 years ago

What is the 24th term if the arithmetic sequence where a1 = 8 and a9 = 56

AnnyKZ [126]

Answer:

$a_{24} = 146$

Step-by-step explanation:

a1 = 8

a9 = 56

Using formula for finding nth term of arithmeric sequence

$a_{n} =a_{1} + (n-1)d$

We have to find 24th term, therefore n = 24

$a_{1}$ is the first term but we are missing d

d is the difference between the two consecutive terms, lets calculate it first

a9 = 56

Using the above given formula for finding d

put n = 9, a9= 56

$a_{9} =a_{1}+ (9-1)d$

56 = 8 + 8d

8d = 48

d = 6

Getting back to main part of finding 24th term

n = 24, d = 6, a1 = 8

put values in nth term formula

$a_{n} =a_{1}+ (n-1)d$

$a_{24} = 8 + (24-1)6$

$a_{24} = 8 + 138$

$a_{24} = 146$

5 0

3 years ago

Find the measure of each numbered angle

Liono4ka [1.6K]

Angle 2 is 360- 258= 102

4 0

3 years ago

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How many feet are in 24 yards? A. 2 B. 72 C. 288 D. 8

Alinara [238K]

1 yard=3 feet
24 yards=
24 yards=24 times yards=24 times (3feet)=24 times 3 times feet=72 times feet
<span>72 feet is the answer</span>

8 0

3 years ago

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Line segment AB has a length of 4 units. It is translated 2 units to the right on a coordinate plane to obtain line segment A′B′

olchik [2.2K]

Answer:

need help asap

Step-by-step explanation:

4 0

3 years ago