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vesna_86 [32]
3 years ago
9

PLS HELP ME ASAP FOR 7, 8, 9. A and B!! (MUST SHOW WORK!!) + LOTS OF POINTS!!

Mathematics
1 answer:
Readme [11.4K]3 years ago
8 0
7. 3.14(12^2 - 10^2)=3.14(144-100) = 3.14(44)=138.16
8. A = piR^2 = 50.24.   R^2 = 50.24/3.14 = 16.   R = 4cm
9a) Perimeter of square is 4*18 = 72.  Perimeter of circle is 2*pi*r.  r=9in
perimeter of circle is then 2*3.14.9 = 56.52.  Difference is 72-56.52 = 15.48
9b) Area of square is 18^2 = 324.
Area of circle is 3.14(9^2) = 254.34.  Difference is the unshaded part
324-254.34 = 69.66in^2
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Technetium-99m is used as a radioactive tracer for certain medical tests. It has a half-life of 1 day. Consider the function T w
Alinara [238K]

Answer:

The expression that represents the number of days until only 10% remains is T((d) 10 %) =100×(\frac{1}{2} )^{3.322}.

Step-by-step explanation:

The equation for half life is of the form

A = A₀×(\frac{1}{2} )^{\frac{t}{h} }.........................................................................(1)

Where

A = Final amount

A₀ = Initial amount

t = Time

h = Half life

For the equation T(d) = 100×2⁽⁻²⁾....................................(2)

We have by comparison with the equation for half life

2 ≡ \frac{t}{h}  and and the equation (2) can be written as

Percentage remaining after 2 half lives is

\frac{A}{A_0} ×100=100×(\frac{1}{2} )^{2 }

However if the half life of Technetium-99m is 6 hours then we have for one day

\frac{A}{A_0} ×100=100×(\frac{1}{2} )^{2 *2}

Therefore an expression that represents the number of days until only 10% remains is

\frac{A}{A_0} ×100=100×(\frac{1}{2} )^{\frac{d}{h}  } = 10 %

(\frac{1}{2} )^{\frac{d}{h}  } =\frac{1}{10}

= ㏑(\frac{1}{2} )^{\frac{d}{h}  }  = ㏑(\frac{1}{10})

= \frac{d}{h}×㏑(\frac{1}{2} ) = ㏑(\frac{1}{10})

\frac{d}{h} = \frac{ln(\frac{1}{10}) }{ln(\frac{1}{2} )} = 3.322

Therefore the expression for the number of days 10 % of Technetium-99m will be remaining is

T((d) 10 %) =100×(\frac{1}{2} )^{3.322}

3 0
4 years ago
The perimeter of an equilateral triangle is 27 centimeters. Find the altitude of the triangle
Naily [24]
7.79cm It is an equilateral triangle so it has 3 equal sides. That means each side is 9cm. <span>
Now draw a line from the top of the equilateral triangle to the base, and dividing it into two. You will have made two smaller triangles, with sides 9, 4.5, and h (the one you want to find). 

A line drawn from the apex of an equilateral triangle to the midpoint of the base is perpendicular to the base, so you can use Pythagoras' Theorem! 

4.5^2 + h^2 = 9^2 
h = sqrt(9^2 - 4.5^2) 
Therefore, the height is 7.79cm (2 decimal places)</span><span>
</span>
4 0
3 years ago
Help please ..........
Bumek [7]
Graph B should be correct
5 0
4 years ago
Please help!!! Please!!!!<br>​
ira [324]

Answer:

Theres a 90 degree angle

90 - 25 = 65 divided by 5 = 13

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3 0
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Emma already has read 6 of 20 books on her summer reading list. What percent of the books on her list has she read already.
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The answer is 30% because 6 divided by 20 is .3 and .3 x 100% = 30%
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