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kherson [118]
3 years ago
12

Cobalt-60 is used for radiotherapy. It has a half-life of 5.26 years. If 4 g of cobalt-60 is administered, how much remains in 3

years? A. 1.2 g B. 2.7 g C. 3.3 g D. 2.1 g E. 0.2 g
Mathematics
1 answer:
NISA [10]3 years ago
7 0

Answer:

B. 2.7 g

Step-by-step explanation:

The half life of a substance is the time taken for the substance to reduce to half of its original amount. It is given by:

A=A_o*(\frac{1}{2})^\frac{t}{t_{1/2}}\\  Where\ A\ is \ the \ amount \ of \ substance\ remaining\ after\ t\ years, \\A_o \ is \ the\ initial\ value\ of \ the\ substance,\ t_{1/2} is\ the\ half\ life\ and\\t\ is\ the\ years\ spent

Given that:

Ao = 4 g, t = 3 years, t(1/2) = 5.26 years. Therefore:

A=A_o*(\frac{1}{2})^\frac{t}{t_{1/2}}\\A=4*(\frac{1}{2} )^\frac{3}{5.26}=4*0.6735=2.7\\ A=2.7\ g

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-----------------------------------------------------------------------------------

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8 0
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Read 2 more answers
Eight times the sum of 8 and some number is 17. What is the number?
OverLord2011 [107]
Edited answer: The number is:  "- 6" .
_______________________________________________

 8 (8 + x) = 16 ;  

in which "x" represents the number for which to be solved ;

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Edit:  64 + 8x = 16 ;

Subtract "64" from each side of the equation:

Edit:   64 + 8x − 64 = 16 <span>− 64 ;

to get:  8x = </span>- 48 ;

Divide EACH SIDE of the equation by "8" ; to isolate "x" on one side of the <span>equation ; and</span> to solve for "x" ;

Edit:     8x / 8 = -48 / 8 ; 

  Edit:    x = - 6 .
______________________________________________
The number is:  "- 6" .
______________________________________________
 Let us check our answer, by plugging in "-6" for "x" in the original equation:
______________________________________________
8 (8 + x) = 16 ; 

→ 8 [8 + (-6) ]  =? 16 ?? ; 

→ 8 (8 − 6 )  =? 16 ?? ; 

→ 8 (2)  =? 16 ?? ; 

→ 16 = ? 16 ??  Yes!
_________________________________________________
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