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nasty-shy [4]
2 years ago
8

Solve the proportion 7/5=21/x (show work/explain how u got it please)

Mathematics
1 answer:
Anvisha [2.4K]2 years ago
5 0

Answer:

x = 15

Step-by-step explanation:

I am going to use the "butterfly" method for proportions

(there is another type of butterfly method that is different, I am not sure if there is another name for this method, sorry!)

\frac{7}{5} = \frac{21}{x}

Multiply the:

- top left by the bottom right

-the top right by the bottom left

and then:

- set them equal to each other

So we will <u>multiply 7 by x and 21 by 5</u> (if this doesn't make sense tell me and I will explain it even more!)

7x = 21 * 5

7x = 105

(Divide both sides by 7) <em>x = 15</em>

Hope this helps, have a nice day! :D <3

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Strontium-90 has a half-life of 28.8 years. If you start with a 300-gram sample of strontium-90,
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Answer:  2.66 × 10⁻¹³

<u>Step-by-step explanation:</u>

First, use the decay formula   A=A_oe^{kt}   where

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  • A₀ is the initial amount (amount you started with)
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Given:

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150=300e^{28.8k}\\\\0.5=e^{28.8k}\\\\ln(0.5)=ln(e^{28.8k})\\\\ln(0.5)=28.8k\\\\\\\dfrac{ln(0.5)}{28.8}=k\\\\\\\large\boxed{-0.0240676=k}\\

Next, input the k-value and the new t-value to solve for A.

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A=300e^{1440(-.0240676)}\\\\\large\boxed{A=2.66\times 10^{-13}}\\

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What is the probability that a point chosen at random in the triangle is also in the blue square?
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2. Find the desired area of the square:

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Step-by-step explanation:

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Step-by-step explanation:

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