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3 years ago

8

After 3 days a sample of radon-222 has decayed to 58% of its original amount.

1 answer:

Rina8888 [55]3 years ago

6 0

The half-life of the radioactive substance can be determined through teh equation ln 2 = k (t 1/2) where k is equal to ln (1/(1-0.58)) / 3. Hence t 1/2 is equal to 2.40 days. To decay to 10% of the original amount, ln (1/0.90) / ( ln2) / 2.40, time is equal to 0.37 days.

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dezoksy [38]

Answer:

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Step-by-step explanation:

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3 years ago

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3 years ago

You buy a dress for $40. The dress was on sale for 20% off. How much is the dress full price?

vladimir1956 [14]

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Step-by-step explanation:

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2 years ago

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steposvetlana [31]

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2 years ago

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Solve the equation 2x^2 + 16x + 21 = 0 to the nearest tenth.

Crank

Answer:

Rounded to the nearest tenth the solutions to the equation are:

x = -1.7 and x = -6.3

Step-by-step explanation:

Since this is a quadratic equation of the form:

$ax^2+bx+c=0$

Use the quadratic formula, which tells you that the solutions would be given by:

$x=\frac{-b+-\sqrt{b^2-4ac} }{2a}$

So in our case, the quadratic formula gives:

$x=\frac{-b+-\sqrt{b^2-4ac} }{2a}\\x=\frac{-16+-\sqrt{16^2-4(2)(21)} }{2*2}\\x=\frac{-16+-\sqrt{88} }{4}$

which gives us two real solutions:

x = - 1.654792

x = -6.345207

Which rounded to the nearest tenth give:

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3 0

3 years ago