Solve using substitution. y = –9x − 1 y = –4x − 6 ( __ , _

A train has an average speed of 18 miles per hour. How long will it take to travel 270 miles?

NARA [144]

I believe the answer is 15 because if you divide 270/18 you get 15

8 0

3 years ago

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2(x + 3) = x - 4 And 4(5x-2)=2(9x+3)

weqwewe [10]

2x+6 - х -4

2x - x = - 4 - 6

x=-10

20x - 8 = 18x +6

20x - 18x = 6 +8

2x = 14

x=7

4 0

3 years ago

A rectangular box with a volume of 272ft^3 is to be constructed with a square base and top. The cost per square foot for the bot

ASHA 777 [7]

Answer:

The dimensions of the box is 3 ft by 3 ft by 30.22 ft.

The length of one side of the base of the given box is 3 ft.

The height of the box is 30.22 ft.

Step-by-step explanation:

Given that, a rectangular box with volume of 272 cubic ft.

Assume height of the box be h and the length of one side of the square base of the box is x.

Area of the base is = $(x\times x)$

$=x^2$

The volume of the box is = area of the base × height

$=x^2h$

Therefore,

$x^2h=272$

$\Rightarrow h=\frac{272}{x^2}$

The cost per square foot for bottom is 20 cent.

The cost to construct of the bottom of the box is

=area of the bottom ×20

$=20x^2$ cents

The cost per square foot for top is 10 cent.

The cost to construct of the top of the box is

=area of the top ×10

$=10x^2$ cents

The cost per square foot for side is 1.5 cent.

The cost to construct of the sides of the box is

=area of the side ×1.5

$=4xh\times 1.5$ cents

$=6xh$ cents

Total cost = $(20x^2+10x^2+6xh)$

$=30x^2+6xh$

Let

C $=30x^2+6xh$

Putting the value of h

$C=30x^2+6x\times \frac{272}{x^2}$

$\Rightarrow C=30x^2+\frac{1632}{x}$

Differentiating with respect to x

$C'=60x-\frac{1632}{x^2}$

Again differentiating with respect to x

$C''=60+\frac{3264}{x^3}$

Now set C'=0

$60x-\frac{1632}{x^2}=0$

$\Rightarrow 60x=\frac{1632}{x^2}$

$\Rightarrow x^3=\frac{1632}{60}$

$\Rightarrow x\approx 3$

Now $C''|_{x=3}=60+\frac{3264}{3^3}>0$

Since at x=3 , C''>0. So at x=3, C has a minimum value.

The length of one side of the base of the box is 3 ft.

The height of the box is $=\frac{272}{3^2}$

=30.22 ft.

The dimensions of the box is 3 ft by 3 ft by 30.22 ft.

7 0

3 years ago

Fiona finds 1 shell on her first day at the beach. every day that wek she finds twice as many shells as she did the day before.

attashe74 [19]

Ok, so on the first day she finds one, the second she finds two, the third four, the fourth eight, the fifth sixteen, the sixth thirty two, and the seventh sixty four. The answer is 64

6 0

3 years ago

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Change 16 2/3 percent to a fraction and simplify. WILL MARK BRAINLIEST

lora16 [44]

Answer:

1/6

Step-by-step explanation:

(16 2/3) / 100

(50/3) / 100

50/300

1/6

7 0

3 years ago

Solve using substitution. y = –9x − 1 y = –4x − 6 ( __ , __ )

Solve using substitution. y = –9x − 1 y = –4x − 6 ( , )