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bixtya [17]
3 years ago
7

Cobalt-56 has a decay constant of 8.77 × 10-3 (which is equivalent to a half life of 79 days). How many days will it take for a

sample of cobalt-56 to decay to 62% of its original value? (At = A0e-kt)
Mathematics
1 answer:
ANEK [815]3 years ago
7 0
So we want to know how long will it take cobalt 56 to decay to 62% to it's original value if we know that one half life is T₁/₂=79 days and it's decay constant is k=8.77*10^-3. The law for radioactive decay is:

N(t)=N₀e^-k*t, where N(t) is the quantity of the material in some time t, N₀ is the original quantity of the material, k is the decay constant, t is time. 

N(t)=0.62*N₀ or 62% of the original value. 
0.62*N₀=N₀e^-k*t, N₀ cancel out and we get:

0.62=e^-k*t

We need to get the time t. We get t if we take the natural logarithm of both sides: 

ln(0.62)=-k*t*ln(e), ln(e)=1 so we have:

ln(0.62)=-k*t

t={ln(0.62)/(-k)} = 54.5. 

Time for cobalt 56 to decay to 62% of its original value is 54.5 days. 
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Ludmilka [50]
Adding: When adding fractions, you want to make sure that the denominator is the same for both fractions. If they are already the same, just add both the numerators to get the answer. For example,
\frac{3 }{5}  +  \frac{1}{5}  =  \frac{4}{5}
If the denominator is different in both fractions, you have to find the least common denominator, or LCD. The LCD is the smallest number that both denominators can multiply into. For example, say you need to find
\frac{1}{6}  +  \frac{1}{3}

Multiply both the numerator and the denominator of (1/3) by 2 to get (2/6). This way, the denominators are the same and you can find the answer.
\frac{1}{6}  +  \frac{2}{6}  =  \frac{3}{6}
In the case that one denominator does not go into the other, find the smallest number they both multiply into. For example,
\frac{1}{3 }  +  \frac{1}{4}
Here, the smallest number that both 4 and 3 multiply into is 12. Multiply both fractions by the correct amount to make both denominators 12. It would then become
\frac{4}{12}  +  \frac{3}{12}  =  \frac{7}{12}
Subtraction: follow the same rules as addition, except subtract the numerators instead of adding them.

Multiplication: multiply both numerators and both denominators.
\frac{2}{3}  \times  \frac{4}{5}  =  \frac{8}{15}
Division: Flip one of the fractions and multiply.
\frac{2}{3}   \div   \frac{4}{5}
Becomes
\frac{2}{3}  \times  \frac{5}{4}  =  \frac{10}{12}  =  \frac{5}{6}
Hope this explains it all. Let me know if you have any questions :)
4 0
3 years ago
What is A, B, and C?
marta [7]

Answer:

A = 46

B = 134

C = 78

Step-by-step explanation:

5 0
3 years ago
Sara is 5 ft 10inches y’all ? To the nearest centimeter how tall is sara? If 1 in equals 2.54 centimeters
Dahasolnce [82]

1 foot = 12 inches.

5 ft x 12 inches per foot = 60 inches.

60 inches + 10 inches = 70 inches.

Sara was 70 inches tall.

Now convert to centimeters:

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Round to nearest centimeter = 178 cm's.

4 0
3 years ago
True or False: The graph below represents the table of values.
Sveta_85 [38]

Answer:

False

Step-by-step explanation:

I would say false;

This graph is really hard to read because of the way it's subdivided but one of the coordinate points is (0,-1) and the line clearly passes through the origin (0,0).

If you have the chance, please tell your teacher to provide better graphs that are actually readable.

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The answer is rational and here is the steps

7 0
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