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Ierofanga [76]
1 year ago
13

Will mark brainliest, need help ASAP!

Mathematics
1 answer:
nikitadnepr [17]1 year ago
5 0

The percentage of the original sample that is left after 115 days is; 23.4733%

<h3>How to calculate the decay percentage?</h3>

Formula for radioactive decay is;

A = A₀ * (1/2)^(t/t_¹/₂)

where;

A = quantity of the substance remaining

A₀ = initial quantity of the substance

t = time elapsed

t_¹/₂ = half life of the substance

Thus;

A/A₀ =  (1/2)^(115/55)

A/A₀ =  0.234733 or 23.4733%

Read more about decay constant at; brainly.com/question/11117468

#SPJ1

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Twice the difference of a number and 9 is equal to three times the sum of the number and 6. Find the number
bezimeni [28]

After modelling the mathematical statement and solving its equivalent mathematical relation, we get x = -36.

<h3>What is Equation Modelling?</h3>

Equation modelling is the process of writing a given mathematical statement in the form of a numeric mathematical expression taking into considerations the operations, constants and other variables.

Given in the question is a number such that twice the difference of a number and 9 is equal to three times the sum of the number and 6.

Assume that the number is x. Now, we will model the equation and solve for x. According to the question, the following mathematical relation represents the statement-

2(x - 9) = 3(x + 6)

2x - 18 = 3x + 18

x = - 36

Therefore, the number is -36.

To solve more questions on Equation modelling, visit the link below-

brainly.com/question/13536824

#SPJ1

8 0
8 months ago
Match the pairs of equations that represent concentric circles. Tiles
Darina [25.2K]
I will explain you and pair two of the equations as an example to you. Then, you must pair the others.

1) Two circles are concentric if they have the same center and different radii.

2) The equation of a circle with center xc, yc, and radius r is:

(x - xc)^2 + (y - yc)^2 = r^2.

So, if you have that equation you can inmediately tell the coordinates of the center and the radius of the circle.

3) You can transform the equations given in your picture to the form (x -xc)^2 + (y -yc)^2 = r2 by completing squares.

Example:

Equation: 3x^2 + 3y^2 + 12x - 6y - 21 = 0

rearrange: 3x^2 + 12x + 3y^2 - 6y = 21

extract common factor 3: 3 (x^2 + 4x) + 3(y^2 -2y) = 3*7

=> (x^2 + 4x) + (y^2 - 2y) = 7

complete squares: (x + 2)^2 - 4 + (y - 1)^2 - 1 = 7

=> (x + 2)^2 + (y - 1)^2 = 12 => center = (-2,1), r = √12.

equation: 4x^2 + 4y^2 + 16x - 8y - 308 = 0

rearrange: 4x^2 + 16x + 4y^2 - 8y = 308

common factor 4: 4 (x^2 + 4x) + 4(y^2 -8y) = 4*77

=> (x^2 + 4x) + (y^2 - 2y) = 77

complete squares: (x + 2)^2  - 4 + (y - 1)^2 - 1 = 77

=> (x + 2)^2 + (y - 1)^2 = 82 => center = (-2,1), r = √82

Therefore, you conclude that these two circumferences have the same center and differet r, so they are concentric.
5 0
3 years ago
Use the equation y+5=x/4 to fill in the missing values in the table below
-Dominant- [34]

Answer:

  1. .
  2. -2
  3. -5
  4. 20
  5. -12

Step-by-step explanation:

hope it helps

5 0
3 years ago
Each student in a classroom has chosen either a green, red, or blue marble and written their initials on it. In addition, some o
scoundrel [369]
A. 2/5 B. 1/3 just like the other person said lol
7 0
2 years ago
You decide to enter in a rowing competition. To train, you go to the boat house and begin rolling down stream. You row for the s
fredd [130]

Answer:

Time spent rowing down stream =100\ seconds

Speed of boat in still water =14\ ms^{-1}

Step-by-step explanation:

Let speed of boat in still water be = x\ ms^{-1}

Speed of current = 10\ ms^{-1}

Speed of boat down stream = \textrm{Speed of boat in still water +Speed of current}= (x+10)\ ms^{-1}

Distance rowed down stream = 2400 m

Time spent rowing down stream = \frac{Distance}{Speed}=\frac{2400}{x+10}\ s = \frac{Distance}{Speed}=\frac{2400}{x+10}\ s

Speed of boat up stream = \textrm{Speed of boat in still water -Speed of current}= (x-10)\ ms^{-1}

Distance rowed up stream = \frac{1}{6} \textrm{ of distance rowed downstream}=\frac{1}{6}\times 2400 = 400\ m

Time spent rowing up stream = \frac{Distance}{Speed}=\frac{400}{x-10}\ s

We know that,

\textrm{Time spent rowing down stream =Time spent rowing up stream}

So,

\frac{2400}{x+10}=\frac{400}{x-10}

Cross multiplying

2400(x-10)=400(x+10)

Dividing both sides by 400

\frac{2400(x-10)}{400}=\frac{400(x+10)}{400}

6(x-10)=x+10

6x-60=x+10

Adding 60 to both sides.

6x-60+60=x+10+60

6x=x+70

Subtracting both sides by x

6x-x=x+70-x

5x=70

Dividing both sides by 5.

\frac{5x}{5}=\frac{70}{5}

∴ x=14

Speed of boat in still water =14\ ms^-1

Time spent rowing down stream =\frac{2400}{14+10}=\frac{2400}{24}=100\ s

3 0
2 years ago
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