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shepuryov [24]
3 years ago
14

Easy to Find, a computer data base, charges $30/h during peak hours to access its records. The charge during off-peak hours is $

12/h. Indigo Research was billed $876.00 last month for 40 hours of access time. Using a system of equations, find the number of hours charged for usage during peak times. A) 16 hours B) 18 hours C) 22 hours D) 24 hours
Mathematics
1 answer:
san4es73 [151]3 years ago
8 0

Let x be the amount of peak time and y be the amount of off-peak time.

30x + 12y = 876.00

x + y = 40

Lets multiply the second equation by 12.

12x + 12y = 480

We can now subtract the two equations from each other to cancel out the y term.

30x + 12y = 876

12x + 12y = 480

18x + 0 = 396

Next, we can solve for x.

18x = 396

x = 22

Lastly, we can plug this value into one of the equations to solve for y.

22 + y = 40

y = 18

So, the number of peak hours was 22 and the number of off-peak hours was 18. The answer is C.

You might be interested in
Two trains travel at right angles to each other after leaving the same train station at the same time. Two hours later they are
Alex787 [66]

Answer:

15 miles per hour is the speed of the slower train.

Step-by-step explanation:

As given in the figure attached,

Let the speed of train 1 is v and train 2 is u.

Therefore, distance traveled in 2 hours by train 1 will be = 2v miles

and distance traveled by train 2 will be = 2u miles

Now we can see in the figure a right angle triangle is formed by the two trains.

AB² + BC² = AC²

(2v)² + (2u)²= (65.30)²

4v² + 4u² = 4264.09

Now we divide this equation by 4

v² + u² = 1066.02

If speed of the slower train is v miles per hour then as per statement of the question.

u = v - 14

v = u + 14

By putting the value of v in the equation

(u + 14)² + u² = 1066

u² + 196 + 28u + u² = 1066

2u² + 28u + 196 = 1066

2u² + 28u + 196 - 1066 = 0

2u² + 28u - 870 = 0

By diving this equation by 2

u² + 14u - 435 = 0

u² + 29u - 15u - 435 = 0

u(u + 29) - 15(u + 29) = 0

(u + 29)(u - 15) = 0

u = -29, 15

Since speed can not be with negative notation so u = 15 miles per hour will be the speed.

Therefore, 15 miles per hour is the speed of the slower train.

5 0
3 years ago
If sin tetha=root3/2, what is cos tetha?​
Minchanka [31]

Answer:

The value of cos Ф is ± \frac{1}{2}

Step-by-step explanation:

There are important rules for sin Ф and cos Ф

  • sin²Ф + cos²Ф = 1
  • sin²Ф = 1 - cos²Ф
  • cos²Ф = 1 - sin²Ф

∵ sin Ф = \frac{\sqrt{3}}{2}

∴ sin²Ф = (\frac{\sqrt{3}}{2})^{2}

∴ sin²Ф = \frac{3}{4}

→ By using the third rule above

∵ cos²Ф = 1 - sin²Ф

∴ cos²Ф = 1 - \frac{3}{4}

∴ cos²Ф = \frac{1}{4}

→ Take square root for both sides

∴ cos Ф = ± \frac{1}{2}

∴ The value of cos Ф is ± \frac{1}{2}

6 0
3 years ago
Please help me
dusya [7]
3(4x - 2) = 2(6x - 3)

12x - 6 = 12x - 6

Add 6 on both sides

12x = 12x

Divide by 12 on both sides

x = x

That means this has infinite solutions. Your answer is B.
4 0
3 years ago
Read 2 more answers
Consider the equality xy k. Write the following inverse proportion: y is inversely proportional to x. When y = 12, x=5.​
skelet666 [1.2K]

Answer:

y=\dfrac {60} {x}   or   xy=60   (depending on your teacher's format preference)

Step-by-step explanation:

<h3><u>Proportionality background</u></h3>

Proportionality is sometimes called "variation".   (ex. " 'y' varies inversely as 'x' ")

There are two main types of proportionality/variation:

  1. Direct
  2. Inverse.

Every proportionality, regardless of whether it is direct or inverse, will have a constant of proportionality (I'm going to call it "k").

Below are several different examples of both types of proportionality, and how they might be stated in words:

  • y=kx      y is directly proportional to x
  • y=kx^2     y is directly proportional to x squared
  • y=kx^3     y is directly proportional to x cubed
  • y=k\sqrt{x}}   y is directly proportional to the square root of x
  • y=\dfrac {k} {x}   y is inversely proportional to x
  • y=\dfrac {k} {x^2}   y is inversely proportional to x squared

From these examples, we see that two things:

  • things that are <u>directly proportional</u> -- the thing is <u>multipli</u>ed to the constant of proportionality "k"
  • things that are <u>inversely proportional</u> -- the thing is <u>divide</u>d from the constant of proportionality "k".

<h3><u>Looking at our question</u></h3>

In our question, y is inversely proportional to x, so the equation we're looking at is the following y=\dfrac {k} {x}.

It isn't yet clear what the constant of proportionality "k" is for this situation, but we are given enough information to solve for it:  "When y=12, x=5."

We can substitute this known relationship pair, and find the "k" that relates this pair of numbers:

<h3><u>Solving for k, and finding the general equation</u></h3>

General Inverse variation equation...

y=\dfrac {k} {x}

Substituting known values...

(12)=\dfrac {k} {(5)}

Multiplying both sides by 5...

(12)*5= \left ( \dfrac {k} {5} \right ) *5

Simplifying/arithmetic...

60=k

So, for our situation, k=60.  So the inverse proportionality relationship equation for this situation is y=\dfrac {60} {x}.

The way your question is phrased, they may prefer the form: xy=60

7 0
2 years ago
Bob and rob in ratio 3:4 and their age 4 years ago was 5:7 find their ages
Trava [24]

Answer:

Present Day:

Bob:Rob:Difference

 3   :  4  :        1

 6   : 12  :       2

4 years ago:

Bob:Rob:Difference

    5 : 7 : 2

6 0
2 years ago
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