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Rudik [331]
3 years ago
13

The half-life of cesium-137 is 30 years. Suppose we have a

Mathematics
1 answer:
VMariaS [17]3 years ago
3 0
(a) If y(t) is the mass (in mg) remaining after t years, then y(t) = y(0) e^{kt}=100e^{kt}.

y(30) = 100 e^{30k} = \frac{1}{2}(100) \implies e^{30k} = \frac{1}{2} \implies k = -(\ln 2) /30 \implies \\ \\
y(t) = 100e^{-(\ln 2)t/30} = 100 \cdot 2^{-t/30}

(b) y(100) = 100 \cdot 2^{-100/30} \approx \text{9.92 mg}

(c)
100 e^{- (\ln 2)t/30} = 1\ \implies\ -(\ln 2) t / 30 = \ln \frac{1}{100}\ \implies\ \\ \\
t = -30 \frac{\ln 0.01}{\ln 2} \approx \text{199.3 years}
 
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3 years ago
Need help!! I can't figure this out
Sidana [21]

9514 1404 393

Answer:

  12. $1,035,057.23

  13. $988,881.23

  14. $7,762.93

  15. $8,686.16

  16. $967,647.66

Step-by-step explanation:

The annuity and amortization formulas are used for problems like this.

  sum of monthly payments = P((1 +r/12)^(12t) -1)/(r/12)

  monthly amount available = P(r/12)/(1 -(1 +r/12)^(-12t))

__

12. The sum of monthly payments of 74, accumulated at 9% compounded monthly for 52 years is ...

  A = ($74)((1 +.09/12)^(12·52) -1)/(.09/12) = $1,035,057.23

__

13. The total of payments is ...

  $74×12×52 = $46,176

So, the interest earned is ...

  $1,035,057.23 -46,176 = $988,881.23

__

14. The amount available in perpetuity is the monthly interest on this account balance.

  $1,035,057.23 × .09/12 = $7,762.93

__

15. The monthly amount available for 25 years is found from the amortization formula:

  A = $1,035,057.23(.09/12)/(1 -(1 +.09/12)^(-12·25)) = $8686.16

__

16. The amortization formula is used for this, too.

  8066 = P(.094/12)/(1 -(1 +.094/12)^(-12·30)) = 0.00833568P

  P = $8066/0.00833568 = $967,647.66

7 0
2 years ago
Interior and Exterior Triangle Angles<br><br> please help asap !!!!
Fiesta28 [93]

Answer:

∠ WUV = 36°

Step-by-step explanation:

The exterior angle of a triangle is equal to the sum of the 2 opposite interior angles.

∠ VWX is an exterior angle of the triangle, thus

8x - 18 = 2x + 8 + 3x + 16

8x - 18 = 5x + 24 ( subtract 5x from both sides )

3x - 18 = 24 ( add 18 to both sides )

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x = 14

Thus

∠ WUV = 2x + 8 = 2(14) + 8 = 28 + 8 = 36°

8 0
2 years ago
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