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3 years ago

I don’t know what to do

Mathematics

2 answers:

barxatty [35]3 years ago

8 0

12.60 because 20% of 15 is 3 subtract 3 from 15 it is 12 and 5% of 12 is .60

sergey [27]3 years ago

4 0

20% of 15 is 12$, and tax is 5% so it comes out to 12.60$
The answer is B

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2 Construct a rational function that will help solve the problem. Then, use a calculator to answer the question.

vaieri [72.5K]

Answer:

Dimension of box:-

Side of square base = 10 in

Height of box = 5 in

Minimum Surface area, S = 300 in²

Step-by-step explanation:

An open box with a square base is to have a volume of 500 cubic inches.

Let side of the base be x and height of the box is y

Volume of box = area of base × height

$500=x^2y$

Therefore, $y=\dfrac{500}{x^2}$

It is open box. The surface area of box, S .

$S=x^2+4xy$

Put $y=\dfrac{500}{x^2}$

$S(x)=x^2+\dfrac{2000}{x}$

This would be rational function of surface area.

For maximum/minimum to differentiate S(x)

$S'(x)=2x-\dfrac{2000}{x^2}$

For critical point, S'(x)=0

$2x-\dfrac{2000}{x^2}=0$

$x^3=1000$

$x=10$

Put x = 10 into $y=\dfrac{500}{x^2}$

y = 5

Double derivative of S(x)

$S''(x)=2+\dfrac{4000}{x^3}$ at x = 10

$S''(10) > 0$

Therefore, Surface is minimum at x = 10 inches

Minimum Surface area, S = 300 in²

7 0

3 years ago

How do you do series with an n

SOVA2 [1]

The problem can be solved step by step, if we know certain basic rules of summation. Following rules assume summation limits are identical.
$\sum{a+b}=\sum{a}+\sum{b}$
$\sum{kx}=k\sum{x}$
$\sum_{r=1}^n{1}=n$
$\sum_{r=1}^n{r}=n(n+1)/2$

Armed with the above rules, we can split up the summation into simple terms:
$\sum_{r=1}^n{40r-21n+8}=n$
$=40\sum_{r=1}^n{r}-21n\sum_{r=1}^n{1}+8\sum_{r=1}^n{1}$
$=40\frac{n(n+1)}{2}-21n^2+8n$
$=20n(n+1)-21n^2+8n$
$=28n-n^2$

=> (a) f(x)=28n-n^2
=> f'(x)=28-2n
=> at f'(x)=0 => x=14
Since f''(x)=-2 <0 therefore f(14) is a maximum
(b) f(x) is a maximum when n=14

(c) the maximum value of f(x) is f(14)=196

4 0

2 years ago

_____ a sequence in which a fixed amount is added on to get the next term

Mariana [72]

Answer: Arithmetic

Explanation:
An Arithmetic Sequence is when a fixed amount is getting added on to the next term, which basically means it is adding a number at a constant rate.

5 0

3 years ago

Math question pre algebra

GalinKa [24]

Answer:

Option B

Step-by-step explanation:

By applying Pythagoras theorem in the given right triangle,

(Hypotenuse)² = (leg 1)² + (leg 2)²

By substituting the values in the given expression,

7² = x² + 2²

49 = x² + 4

x² = 49 - 4

x² = 45

x = √45

x = 3√5

x = 6.7 ft

Option B will be the correct option.

3 0

3 years ago

An hourglass, composed of two identical cones, is 12 cm tall. The radius of each cone is 3 cm. If you want to fill the bottom ha

EleoNora [17]

The volume of a cone is V= (1/3)pi r²h
it was given
h=12cm
radius=3cm
the volume of the first cone is V1= 1/3)pi r²h1
where h1= h/2=6cm
so its volume is V1=1/3)xpix3²x6=56.52cm^3

and since the two cones are identical so V1=V2=56.52cm^3,
we need 56.52cm^3 or salt

6 0

3 years ago