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DerKrebs [107]
4 years ago
13

In four years, 40% of a radioactive element decays. Find its half-life. Round to one decimal place.

Mathematics
2 answers:
Misha Larkins [42]4 years ago
7 0

Answer:

T(Half Life) = 5.42 s

Step-by-step explanation:

Given :

t = 4years

[R]₀(Initial Concentration) = 100(say)

[R](Concentration Left after time t=4yrs) = 100 - 40 = 60

We know that,

k = 2.303 / t (log{[R]₀/[R]})

where k = rate constant

k = 2.303 / t (log[100/60])

k = 2.303 / 4 (log[10] - log[6])

k = 2.303 / 4 (1 - 0.7781)

k = 2.303 / 4 (0.2219)

k = 0.5110 / 4

k = 0.1277          --------(i)

Now, to find its half life,

We know that,

T(Half Life) = 0.693 / k

T = 0.693 / 0.1277

T = 5.42 years

White raven [17]4 years ago
5 0

To find the answer, use k = \frac{2.303 }{ 4} (log\frac {100 }{ 40}) , and then use the equation t=\frac{.693}{k} To find it's half life.

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use pythagoren theorem
first convert the units

4'=4 feet
8''=8 inches
convert to inches
4 feet times 12=48 inches

so
pythagorea theorem is
a^2+b^2=c^2
c=hypotonuse
a and b are legs
in a right triangle

8 and 48 are the legs
fidn hypotonuse

8^2+48^2=c^2
64+2304=c^2
2368=c^2
8√37=c
aprox
48.66=c
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6 0
3 years ago
(08.03 MC)
tester [92]
The trick here is to notice that all 3 terms can be div. by 2:

2(x^2 + x - 12)

Note that -12 factors into -3 * 4 or -4 * 3.  Thus,

x^2 + x - 12 = (x-4)(x+3), and so <span>2x2 + 2x − 24 = 2(x-4)(x+3).</span>
7 0
3 years ago
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You’re rectangular 12 feet long and 8 feet wide. Your friend’s rectangular vegetable garden 50 feet long and 10 feet wide are th
igor_vitrenko [27]

Answer:

No

Step-by-step explanation:

For shapes to be similar, their ratios of length-to-length and width-to-width must be the same. When you divide the larger length by the smaller length and the larger width by the smaller width, do you get the same number? No, so these rectangles are not similar.

5 0
3 years ago
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A triangle shaped paper’s height is 18 cm and width is 10 cm. Find the hypotenuse of the paper.
vodomira [7]
The hypotenuse is 20.59. 10^2+18^2=C^2
7 0
3 years ago
If f(x) = 2x^4, then f'(3) =
valkas [14]

To find f'(3) (f prime of 3), you must find f' first.  f' is the derivative of the function f(x).

Finding the derivative of f(x) = 2x⁴ requires the use of the power rule.

The power rule for derivatives is \frac{d}{dx} [x^{n} ] =nx^{n-1}.  In other words, you bring the exponent forward and multiply it by the coefficient of the term, and then you subtract 1 from the original exponent.

f'(x) = \frac{d}{dx}(2x⁴)

f'(x) = 2(4)x³

f'(x) = 8x³

Now, to find f'(3), plug 3 into your derivative.

f'(3) = 8(3)³

f'(3) = 216

<h3>Answer:</h3>

f'(3) = 216

6 0
3 years ago
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