Number of students = 26
Number of students without siblings = 4
⇒ Number of students with at least one siblings = 26 - 4 = 22
Number of students with brothers = 17
Number of students with sisters = 7
⇒ Number of students with both a brother and a sister = 17 + 7 - 22 = 2
P(student has a brother, given that they have a sister) = 2/7
Answer: 2/7
Answer:
The new position is 190 feet below sea
Step-by-step explanation:
240-50=190
Answer:
x = -14
Step-by-step explanation:
4x + 8 = 3x - 6
4x = 3x - 14
x = -14
The amount of substance left of a radioactive element of half life,
![t_{\frac{1}{2}}](https://tex.z-dn.net/?f=t_%7B%5Cfrac%7B1%7D%7B2%7D%7D)
after a time, t, is given by:
![N(t)=N_0\left( \frac{1}{2} \right)^ \frac{t}{t_{ \frac{1}{2} }}](https://tex.z-dn.net/?f=N%28t%29%3DN_0%5Cleft%28%20%5Cfrac%7B1%7D%7B2%7D%20%5Cright%29%5E%20%5Cfrac%7Bt%7D%7Bt_%7B%20%20%5Cfrac%7B1%7D%7B2%7D%20%7D%7D)
Given that <span>potassium-40 has a half life of approximately 1.25 billion
years.
The number of years it will take for 0.1% of potassium-40 to remain is obtained as follows:
![0.1=100\left( \frac{1}{2} \right)^ \frac{t}{1.25}} \\ \\ \Rightarrow\left( \frac{1}{2} \right)^ \frac{t}{1.25}}=0.001 \\ \\ \Rightarrow\frac{t}{1.25}\ln\left( \frac{1}{2} \right)=\ln(0.001) \\ \\ \Rightarrow \frac{t}{1.25}= \frac{\ln(0.001)}{\ln\left( \frac{1}{2} \right)} =9.966 \\ \\ t=9.966(1.25)=12.5](https://tex.z-dn.net/?f=0.1%3D100%5Cleft%28%20%5Cfrac%7B1%7D%7B2%7D%20%5Cright%29%5E%20%5Cfrac%7Bt%7D%7B1.25%7D%7D%20%5C%5C%20%20%5C%5C%20%5CRightarrow%5Cleft%28%20%5Cfrac%7B1%7D%7B2%7D%20%5Cright%29%5E%20%5Cfrac%7Bt%7D%7B1.25%7D%7D%3D0.001%20%5C%5C%20%20%5C%5C%20%5CRightarrow%5Cfrac%7Bt%7D%7B1.25%7D%5Cln%5Cleft%28%20%5Cfrac%7B1%7D%7B2%7D%20%5Cright%29%3D%5Cln%280.001%29%20%5C%5C%20%20%5C%5C%20%5CRightarrow%20%5Cfrac%7Bt%7D%7B1.25%7D%3D%20%5Cfrac%7B%5Cln%280.001%29%7D%7B%5Cln%5Cleft%28%20%5Cfrac%7B1%7D%7B2%7D%20%5Cright%29%7D%20%3D9.966%20%5C%5C%20%20%5C%5C%20t%3D9.966%281.25%29%3D12.5)
Therefore, </span><span>the maximum age of a fossil that we could date using 40k is
12.5 billion years.</span>