The radioactive isotope of lead, Pb-209, decays at a rate proportional to the amount present at time t and has a half-life of 3.3 hours. If 1 gram of this isotope is present initially, how long will it take for 90% of the lead to decay? (Round your answer to two decimal places.)
Answer:
It will take 10.96 hours for 90% of the lead to decay.
Step-by-step explanation:
The radioactive isotope of lead, Pb-209, decays at a rate proportional to the amount present at time t
This means that the amount can be modeled by the following function:
[tex]A(t) = A(0)e^{-rt}[/tex]
In which A(0) is the initial amount and r is the decay rate.
Has a half-life of 3.3 hours.
This means that [tex]A(3.3) = 0.5A(0)[/tex]. We use this to find r.
[tex]A(t) = A(0)e^{-rt}[/tex]
[tex]0.5A(0) = A(0)e^{-3.3r}[/tex]
[tex]e^{-3.3r} = 0.5[/tex]
[tex]\ln{e^{-3.3r}} = \ln{0.5}[/tex]
[tex]-3.3r = \ln{0.5}[/tex]
[tex]r = - \frac{\ln{0.5}}{3.3}[/tex]
[tex]r = 0.21[/tex]
So
[tex]A(t) = A(0)e^{-0.21t}[/tex]
How long will it take for 90% of the lead to decay?
This is t for which [tex]A(t) = 0.1A(0)[/tex], that is, 100 - 90 = 10% of the initial amount.
[tex]A(t) = A(0)e^{-rt}[/tex]
[tex]0.1A(0) = A(0)e^{-0.21t}[/tex]
[tex]e^{-0.21t} = 0.1[/tex]
[tex]\ln{e^{-0.21t}} = \ln{0.1}[/tex]
[tex]-0.21t = \ln{0.1}[/tex]
[tex]t = -\frac{\ln{0.1}}{0.21}[/tex]
[tex]t = 10.96[/tex]
It will take 10.96 hours for 90% of the lead to decay.
AHH IM SORRY!!Twenty-four out of forty pies at the bake sale are chocolate pies. What percent is chocolate.
Answers
24%
40%
60%
75%
Ik I should be figuring it out on my own but my brain is fried
Answer:
60%
Step-by-step explanation:
A park ranger wants to know the average time it takes hikers to hike a trail. There is an average of 1,245 hikers on the trail in a year. How can he find a reasonable estimate for the amount of time it takes to hike the trail? A time any hiker on the trail and use that time
B time himself on the trail and use that time
C time 100 hikers and average their times
D time 3 hikers and average their times
Answer:
B
Step-by-step explanation:
the reason why is a bigger sample size and a different types of people in a 100 than 3 or than himself
It’s due late tonight can some pls help me pass
Answer:
Table A
Step-by-step explanation:
plugging the x values into the rule f(x)=-2x gets you
f(-3)= 6
f(-1)= 2
f(1)= -2
f(3)= -6
PLS HELP with this problem !!!
Answer:
god
Step-by-step explanation:
Order of operations with integers
Calculate: 8-4(2+5²)/12
Answer:
Step-by-step explanation:
8-4(2+ (5)2) /12
8-4 (2+25)/12
8-4 (27)/12
4(27) /12
108/12
= 9
The highest degree of academic achievement in the American education system is a __________ degree.
A.
bachelor’s
B.
doctorate
C.
master’s
D.
secondary
A carpenter leans a 20-foot ladder against a building so that an angle of 60° is formed between the ladder and the ground. How many feet away from the
building is the bottom of the ladder?
O 10/3ft
O 20 ft
O 20V2 ft
O 10 ft
Answer:
The foot of the ladder is
10
feet away from the base of the wall.
Step-by-step explanation:
The distance between building and the bottom of the ladder is option (D) 10 ft
What is Trigonometric function?In mathematics, the trigonometric functions are real functions which relate an angle of a right-angled triangle to ratios of two side lengths.
Given,
Length of the ladder = 20 foot
Angle between the ladder and the ground = 60 degrees
Draw the figure using the given data
We know,
cos θ = Adjacent side / Hypotenuse
cos 60 = [tex]\frac{x}{20}[/tex]
x = 20 × cos 60
x = 10 ft
Hence, the distance between building and the bottom of the ladder is option (D) 10 ft
Learn more about Trigonometric function here
https://brainly.com/question/6904750
#SPJ2
Choose Reason#5
Reasons
ABCD
1 Given
2
3. and BIR
3
4
4. Alternate Interior Angles Theorem
5
S. SABD SCO
A AAS Theorem
SAS Postulate
ASA Postulate
SSS Postulate
PLEASE HELP QUICK
Answer:
ASA!
Step-by-step explanation:
I'll explain why in the comment
Randy bought 3 identical shirts and paid a sales tax of $2.84. The total cost was $50.18. What was the cost of each shirt?
Answer:
$15.78
Step-by-step explanation:
I) Remove tax:
$50.18 - $2.84 = $47.34
II) Construct an equation to find the cost of each shirt:
47.34 = 3s
III) Solve:
Divide each side by 3:
15.78 = s
Each shirt costed $15.78
Answer:
15.78
Step-by-step explanation:
I TYPED IN THE ANSWER CAN SOMEONE CORRECT IF IT IS WRONG?
Answer: No you are not wrong
Step-by-step explanation:
Rewrite -8x-2y=6 into slope intercept
Find an equation parallel to 3x + 2y = –4.
Answer:
I think the answer is 2y + 3x = -4 but I think is wrong.
Step-by-step explanation:
you just move the numbers to the opposite side.
AM I RIGHT PLEASE HELP will mark BRAINLIEST
Answer:
Yes
Step-by-step explanation:
BC ll EF
Solve: 8p = 24
A p = 192
B p = 16
p=3
D p = 32
Answer:
p=3
Step-by-step explanation:
Step-by-step explanation:
8p = 24
p=3
HOPE it helps you ..
Help me please if you can
Answer:
<D=<J
Step-by-step explanation:
The first answer is the only correct statement. In geometry, congruent angles are shown through the number of arcs on the vertex of an angle. For example, if two different angles both had three arcs on the vertex, then those two angles are congruent. In this figure, both <D and <J have 4 arcs, which means they are congruent. Additionally, both angles are opposite of a line that measures 25 inches. If two angles are opposite of congruent lines, then the angles are also congruent.
What's the slope of the line in the graph above?
Question 9 options:
A)
–3∕5
B)
–5∕3
C)
5∕3
D)
3∕5
Answer:
C.5/3
Step-by-step explanation:
5 up and 3 to the side
Answer:
C is correct
Step-by-step explanation:
Looking out for me balcony the angle of elevation to the top of the next building is approximately 22° in the English depression to the bottom of the building approximately 29° if the building is 200 feet away how tall is the building?
I will give brainliest to whoever solves it right. hint its not 80.7 feet
Answer:
Step-by-step explanation:
[tex]\tan22=h_1/200,\ \tan29=h_2/200
h_2+h_1=200(\tan29+\tan22)
H\approx 191.667ft
H\approx 191’ 8”
Help please my teacher wont let me leave till im done with this question
Answer:
To find the x intercept substitute 0 for y and solve for x. To find the y intercept substitute 0 for x and solve for y.
X intercept: (-2,0)
Y intercept: (0,5/2)
im not sure if you looking for the X and Y intercept for the second equation but if you are the
X intercept: (5/2,0)
Y intercept: (0,-5)
Answer:
hey vanessa its me caden....
Step-by-step explanation:
(sorry i cant help with the problem....)
Need help please only searious answers.
Answer:
answer 3
Step-by-step explanation:
Hope this helps you out
Jonny
had 7 cakes. He eats 1/12 of
his total amount of cakes. How much
cake does he have left?
Answer:
6 11/12
Step-by-step explanation:
Pam has 24 marbles she put 3 fourth in a jar how many marbles does she have
Answer:
6 outside
18 in the jar
Step-by-step explanation:
If anyone knows please help me
Answer:
Step-by-step explanation:
Standard form of a circle is given by,
(x - a)² + (y - b)² = r²
Here, (a, b) is the center and 'r' is the radius of the circle.
For a circle having center (8, -4) and radius r = 1
Equation of the circle will be,
(x - 8)² + (y + 4)² = 1²
(x - 8)² + (y + 4)² = 1
Option (1) is the answer.
Question (2)
Circle with the center (-1, 0) and a point (2, -4) on it,
Radius of the circle = Distance between the center and the given point on circumference
= [tex]\sqrt{(x_1-x_2)^2+(y_1-y_2)^2}[/tex]
= [tex]\sqrt{(-1-2)^2+(0+4)^2}[/tex]
= [tex]\sqrt{9+16}[/tex]
= 5
Therefore, equation of the circle will be,
(x + 1)² + (y - 0)² = 5²
(x + 1)² + y² = 25
How to solve please help.
[tex]7 x^{2} 8x\alpha \sqrt{x} 7[/tex]
You are saving up money to buy a new ipad. You begin with $25, and are able to save $40 each month. Write an
equation to determine the amount of money you have after x months.
Pleaseee help me!!! Needed by 10:35
Answer:
567
Step-by-step explanation:
Answer The Question for Brainliest
Answer:
turn it 90 degrees, hope this helps
Step-by-step explanation:
Answer:
so go to the 120 degree line and make sure the line is straight across from zero and thin dray a line going from 120 down to the bottom of where the zero is
Step-by-step explanation:
there are 960 pages in a book. each page contains 25lines. how many lines are there in the book
Answer:
24000 Lines.
Step-by-step explanation:
960x25=24000
Answer:
24,000
Step-by-step explanation:
just multiply 960 x 25
If f(x)=47x-55, then f(f^-1(x))=?
In ΔRST, the measure of ∠T=90°, the measure of ∠S=35°, and ST = 2.9 feet. Find the length of RS to the nearest tenth of a foot.
Answer:
3.5
Step-by-step explanation:
i'm smart
The Question is in the attachment below
Answer:
Step-by-step explanation:
It is J I’m pretty sure