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vodomira [7]
3 years ago
13

The​ half-life of​ carbon-14 is 5600 years. if a piece of charcoal made from the wood of a tree shows only 62​% of the​ carbon-1

4 expected in living​ matter, when did the tree​ die?
Mathematics
1 answer:
sasho [114]3 years ago
5 0

The amount of carbon-14 present obeys an exponential decay law.

 

A(t) = A(0)e-^kt

 

Get k from the half-life:

 

0.5 = 1e-^k(5600)

 

k = ln(0.5) / (-5600 years) = 1.2378 x 10^-4 years^-1

 

If only 73% of the carbon-14 remains after time T, then

 

0.73 = 1e^-kT

 

T = ln(0.73) / (-1.2378 x 10^-4 years^-1) = 2542.5 years

 

The tree has been dead for about 2542.5 years.

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ratelena [41]

Answer:

We need to remember that we have independent events when a given event is not affected by previous events, and we can verify if two events are independnet with the following equation:

P(A \cap B) = P(A) *P(B)

For this case we have that:

P(A) *P(B) = 0.01*0.02= 0.0002

And we see that 0.0002 \neq P(A \cap B)

So then we can conclude that the two events given are not independent and have a relationship or dependence.

Step-by-step explanation:

For this case we can define the following events:

A= In a certain computer a memory failure

B= In a certain computer a hard disk failure

We have the probability for the two events given on this case:

P(A) = 0.01 , P(B) = 0.02

We also know the probability that the memory and the hard drive fail simultaneously given by:

P(A \cap B) = 0.0014

And we want to check if the two events are independent.

We need to remember that we have independent events when a given event is not affected by previous events, and we can verify if two events are independnet with the following equation:

P(A \cap B) = P(A) *P(B)

For this case we have that:

P(A) *P(B) = 0.01*0.02= 0.0002

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8 0
2 years ago
Pythagorean theorem
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Answer:

b=20 yards

Step-by-step explanation:

15^2+x^2=25^2

225+x^2=625

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5 0
2 years ago
What is the value of b?
tresset_1 [31]

Answer:

17

Step-by-step explanation:

Using the law of cosines in ΔABC

b² = a² + c² - (2ac cosB) ← substitute in values

   = 25² + 28² - (2 × 25 × 28 × cos36.9°)

   = 625 + 784 - 1400 cos36.9°

   = 1409 - 1400 cos36.9° ( Take the square root of both sides )

b = \sqrt{1409-1400cos36.9} ≈ 17 ( nearest whole number )

   

8 0
3 years ago
Nine more than half of a number is 21
pogonyaev
I assume you're looking for the number:
0.5n + 9 = 21
- 9
0.5n = 12
÷ 0.5
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3 0
3 years ago
Explain how to subtract three digit numbers when u need to regroup hundreds and tens
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when you subtract numbers with three digits its almost exactly the same as regular subtracting but with decimals.


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