strontium-90 is a radioactive material that decays according to the function A(t)=A0e−0.0244t, where A0 is the initial amount present and A is the amount present at time t (in years). Assume that a scientist has a sample of 400 grams of strontium-90.
(a) What is the decay rate of strontium-90?
(b) How much strontium-90 is left after 30 years?
(c) When will only 100 grams of strontium-90 be left?
(d) What is the half-life of strontium-90?
(a) The decay rate of strontium-90 is nothing%.
(Type an integer or a decimal. Include the negative sign for the decay rate.)
Answer:
Step-by-step explanation:
The decay rate of strontium-90 is -.0244 as given.
For b., we have to use the formula to find out how much is left after 30 years. This will be important for part d.
[tex]A(t)=400e^{-.0244(30)}[/tex] which simplifies a bit to
A(t) = 400(.4809461353) so
A(t) = 192.4 g
For c., we have to find out how long it takes for the initial amount of 400 g to decay to 100:
[tex]100=400e^{-.0244t}[/tex]. Begin by dividing both sides by 400:
[tex].25=e^{-.0244t[/tex] and then take the natural log of both sides:
[tex]ln(.25)=lne^{-.0244t[/tex] . The natural log and the e cancel each other out since they are inverses of one another, leaving us with:
ln(.25) = -.0244t and divide by -.0244:
61.8 years = t
For d., we figured in b that after 30 years, 192.4 g of the element was left, so we can use that to solve for the half-life in a different formula:
[tex]A(t)=A_0(.5)^{\frac{t}{H}[/tex] and we are solving for H. Filling in:
[tex]192.4=400(.5)^{\frac{30}{H}[/tex] and begin by dividing both sides by 400:
[tex].481=(.5)^{\frac{30}{H}[/tex] and take the natural log of both sides, which allows us to pull the exponent out front. I'm going to include that step in with this one:
ln(.481) = [tex]\frac{30}{H}[/tex] ln(.5) and then divide both sides by ln(.5):
[tex]\frac{ln(.481)}{ln(.5)}=\frac{30}{H}[/tex] and cross multiply and isolate the H to get:
[tex]H=\frac{30ln(.5)}{ln(.481)}[/tex] and
H = 28.4 years
Simplify the algebraic expression by combining like (or similar) terms.
2x−y2+3−3y2+2x+1
Answer:
-4y^2 + 4x +4
Step-by-step explanation:
add -y^2 and -3y^2 = -4y^2
add 2x + 2x = 4x
add 3+1 = 4
and then rearrange
Can someone please help with 25 , please put the way you got it. Please no links it’s serious
Answer:
X * 0.8 = $64
x = $80
Step-by-step explanation:
10) Find three numbers whose product is -72. You may use integers from -10 to 10. Give two
examples
Answer:
Step-by-step explanation:
-8 * 9 * 1
If you are going to get - 72, you need to have an odd number of minus signs.
4 * 3 * - 6
You must be careful of the limits. You can't use something like 36 * 2 * 1 because the numbers don't fall within +/- 10
You could use 6*6*-2
PLZ ANSWER ASAP
(look at images below, from khan)
Answer:
D Replace on equation with sum /difference of both equations
The systems are still the same
Step-by-step explanation:
5x + y = 3
4x - 7y = 8
Subtract the second equation from the first
5x + y = 3
-(4x - 7y = 8)
-----------------
x +8y = -5
The second equation in system B is the first equation in system a minus the second equation in system A
We added the same thing to each side of the equation so the the system is still the same
Which of the following is correctly written in Standard Form? −3x + 7y = 12, y = 3/7x + 6 ,5x − 4y = 9 ,3/7x + 2y =9
Use the distributive property to simplify
the equation below.
с
8(2a + 4b - c)
[? ]a + [ ]b - [
[ ]
Answer:
16a +32b - 8c
Step-by-step explanation:
8(2a + 4b - c)
Distribute
8*2a + 8*4b+ 8*(-c)
16a +32b - 8c
Answer:
16a + 32b - 8c
Step-by-step explanation:
You bring 8 inside the parenthesis and then multiply it with everything. so for a you put 16, b you put 32 and c you put 8
A painter can paint 36 feet of molding per hour. How many inches of molding can he paint per hour?
Answer:
432 inches
Step-by-step explanation:
We need to convert feet to inches
1 ft = 12 inches
36 ft * 12 inches/ 1 ft = 432 inches
A basic cellular package costs $30/month for 60 minutes of calling with an additional charge of $0.40/minute beyond that time. The cost function C (2) for using x minutes would be • If you used 60 minutes or less, i.e. if if x < 60, then C (x) = 30 (the base charge). If you used more than 60 minutes, i.e. (x – 60 minutes more than the plan came with, you would pay an additional $0.40 for each of those (x – 60 minutes. Your total bill would be C (x) = 30 + 0.40 (x – 60). If you want to keep your bill at $50 or lower for the month, what is the maximum number of calling minutes you can use? minutes. The maximum calling minutes you can use is ? Number
Answer:
The maximum number of minutes to keep the cost at $50 or less is 110 minutes
Step-by-step explanation:
Given
[tex]C(x) = 30[/tex] ---- [tex]x < 60[/tex]
[tex]C(x) = 30 + 0.40(x - 60)[/tex] --- [tex]x \ge 60[/tex]
Required
[tex]C(x) = 50[/tex] ---- find x
We have:
[tex]C(x) = 30 + 0.40(x - 60)[/tex]
Substitute 50 for C(x)
[tex]50 = 30 + 0.40(x - 60)[/tex]
Subtract 30 from both sides
[tex]20 = 0.40(x - 60)[/tex]
Divide both sides by 0.40
[tex]50 = x - 60[/tex]
Add 60 to both sides
[tex]110 = x[/tex]
[tex]x =110[/tex]
Larry made 14 baskets out of 21 attempts in a recent basketball game. If Scott attempted 24 baskets and made the same proportion of baskets as Larry, how many baskets did Scott make?
Scott made
baskets.
Answer:
16 baskets
Step-by-step explanation:
Create a proportion where x is the number of baskets that Scott made:
[tex]\frac{14}{21}[/tex] = [tex]\frac{x}{24}[/tex]
Cross multiply and solve for x:
21x = 336
x = 16
So, Scott made 16 baskets.
the polygons in each pair are similar find the scale factor smaller figure to the larger
Answer:
smaller figure/larger figure = ½
Step-by-step explanation:
The scale factor = any of the side length of the smaller figure / the corresponding side length of the larger figure
Side length of smaller figure = 3
Corresponding sides length of larger figure = 6
Scale factor = smaller figure/larger figure = 3/6
Simplify
Scale factor = smaller figure/larger figure = ½
Instructions: Given the vertex of a quadratic function, find the axis
of symmetry.
Vertex: (5,7)
Taking into account the definition of axis of simmetry and vertexn the axis of symmetry is x = 5.
So, first of all, you must know what a quadratic function is. Every quadratic function can be expressed as follows:
f(x) = a*x² + b*x + c
where a, b and c are real numbers.
Axis of symetryThe graph of a quadratic function is a parabola. Every parabola is a symmetric curve with respect to a horizontal line called the axis of symmetry.
That is, the axis of symmetry is an imaginary line that passes through the middle of the parabola and divides it into two halves that are equal of each other.
In other words, the axis of symmetry of a parabola is a vertical line that divides the parabola into two equal halves and always passes through the vertex of the parabola.
VertexThe point of intersection of the axis of symmetry with the parabola is called the vertex.
The axis of symmetry always passes through the vertex of the parabola. The x-coordinate of the vertex is the equation of the axis of symmetry of the parabola.
SummaryBeing the vertex of the quadratic function (5,7), where the vertex on the x-axis has a value of 5 and on the y-axis a value of 7, the axis of symmetry is x = 5.
Learn more with this examples:
https://brainly.com/question/2799442?referrer=searchResultshttps://brainly.com/question/20862832?referrer=searchResultshttps://brainly.com/question/15266651?referrer=searchResultsHi! I would appreciate if you could solve this for me. The question I need help with is question 41. Thank you. :)
Answer:
Expression: 7+7+9.5+6+9.5
Evaluation: 39 cm
Step-by-step explanation:
Let's write the numerical expression for the figure to the right. The perimeter is the addition of all sides of the figure. Therefore, we write 7+7+9.5+6+9.5 for our expression.
Now, to evaluate the expression, we just add them together. 7+7+9.5+6+9.5=39 cm.
Express b+1/3b-2 with “b” as the subject
Answer:
b = [tex]\frac{1+2a}{3a-1}[/tex]
Step-by-step explanation:
Given
a = [tex]\frac{b+1}{3b-2}[/tex] ( multiply both sides by 3b - 2 )
a(3b - 2) = b + 1 ← distribute left side
3ab - 2a = b + 1 ( subtract b from both sides )
3ab - b - 2a = 1 ( add 2a to both sides )
3ab - b = 1 + 2a ← factor out b from each term on the left side
b(3a - 1) = 1 + 2a ( divide both sides by 3a - 1 )
b = [tex]\frac{1+2a}{3a-1}[/tex]
Answer:
[tex]→a = \frac{(b + 1)}{(3b - 2)} \\ a(3b - 2) = (b + 1) \\ 3ab - 2a = b + 1 \\ 3ab - b = 2a + 1 \\ b(3a - 1) =( 2a + 1) \\ \boxed{b = \frac{(2a + 1)}{(3a - 1)} }✓[/tex]
b = (2a+1)/(3a-1) is the right answer.Find the value of x.
A. 4
B. 2
C. 3
D. 6
Answer:
b
Step-by-step explanation:
2x4=8 3x2=6 2x2=4
there all diviseble by 2
therfore ur answer is b
Answer:
the answer is 4
Step-by-step explanation:
WHAT GRAPH BEAST REPRESENTS THE FOLLOWING SITUATION? aS X INCREASES, Y DECREASES R=-0.41
Answer:
there is no graph here
Step-by-step explanation:
Example 2.20
Solution
After 7% discount, Faizal get RM1,930 from a bank. He then promised to pay the bank RM2,000
after x days. Determine the value of x.
Kaspersk
Th
The period of days (value of x) for which Faizal promised to pay the bank RM 2,000 after getting 7% discounted present value of RM 1,930 is 180 days.
The value of x is the period of days (number of days) that the loan from the bank will last before Faizal, who received RM 1,930 discounted at 7%, would repay the bank the principal and interest of RM 2,000.
This implies that Faizal is paying an interest of RM 70 (RM 2,000 - RM 1,930), since he borrowed RM 1,930 and will repay RM 2,000.
Data and Calculations:
Present value of loan received = RM 1,930
Discount rate per year = 7%
Future value of the loan to be repaid to the bank = RM 2,000
Interest expense for one year based on 7% = RM 140 (RM 2,000 x 7%)
Interest expense for 180 days or 6 months = RM 70 (RM 2,000 - RM 1,930) or (RM 2,000 x 7%) x 180/360
Interest expense that equals RM 70 will be half of a year or 180 days (RM 140 * 180/360)
Thus, the period of days (x) that will lapse for Faizal to repay the bank is 180 days or half of a year (6 months).
Learn more about time period of a loan here: https://brainly.com/question/19118285
The probability of winning a raffle is 2/5. What is the probability of not winning the raffle?
0
3/5
2/5
Answer:
3/5
Step-by-step explanation:
um 3/5+2/5 = 1
What are the values of a, b, and c in the quadratic equation 0 = one-halfx2 – 3x – 2?
a = one-half, b = 3, c = 2
a = one-half, b = –3, c = –2
a = one-half, b = 3, c = –2
a = one-half, b = –3, c = 2
Answer:
b
Step-by-step explanation:
ax^2+bx+c=0
1/2x^2-3x-2=0
Answer:
B
Step-by-step explanation:
What is x: |3x-1| = 4
Step-by-step explanation:
3x-1=4
3x=4+1
3x=5
x=5/3
Answer:
x = 5/3 x = -1
Step-by-step explanation:
|3x-1| = 4
There are two solutions, one positive and one negative
3x-1 =4 and 3x-1 = -4
Add 1 to each side
3x-1+1 = 4+1 3x-1+1 = -4+1
3x = 5 3x = -3
Divide by 3
3x/3 = 5/3 3x/3 = -3/3
x = 5/3 x = -1
Which graph has the solutions -1 and 4?
a.
On a coordinate plane, a parabola opens up and goes through (negative 4.2, 0) and (0, negative 1).
c.
On a coordinate plane, a parabola opens up and goes through (negative 4, 0) and (1, 0).
b.
On a coordinate plane, a parabola opens up and goes through (0, negative 3) and (4.5, 0).
d.
On a coordinate plane, a parabola opens up and goes through (0, negative 1) and (4, 0).
Please select the best answer from the choices provided
A
B
C
D
Answer:
graph d
in graph d, the line intersects the x axis twice at (-1,0) and (4,0), so those two are the solutions of the graph
of a loaf of brown bread costs R6, how much will 4 halves cost?
Answer:
R12
Step-by-step explanation:
Answer: R12
Explanation:
Cost of 1 loaf = R6
Cost of 4 halves = 6/2×4
= 6 × 2
= R12
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What is the product of these two binomials?
(x2 - 5)(2x - 1)
Select the correct answer.
o 2x3 - x2 + 10x - 5
O 2x3 - x2 - 10x-5
o 2x3 - x2 - 10x + 5
o 2x3 - x2 + 10x + 5
Answer:
2x³ - x² - 10x + 5
Step-by-step explanation:
Use FOIL method.
(x² - 5) (2x - 1) = x²*2x +(x²)*(-1) + (-5)*(2x) + (-5)*(-1)
= 2x³ - x² - 10x + 5
16 • (14) =
-9 • (-8) =
- 13 • 7
Answer:
16×14 = -9×(-8) = -13×7
Falso
Step-by-step explanation:
Please help with Question 2b
Answer:
MUST BE IN HLA, NOT FROM C TO ASSEMBLY.
PROGRAM 6: Same
Write an HLA Assembly language program that implements a function which correctly identifies when all four parameters are the same and returns a boolean value in AL (1 when all four values are equal; 0 otherwise). This function should have the following signature:
procedure theSam
Air is being pumped into a spherical balloon at a rate of 5 cm^3/min. Determine the rate at which the radius of the balloon is increasing when the diameter of the balloon is 20 cm
0.08 cm/min
Step-by-step explanation:
Given:
[tex]\dfrac{dV}{dt}=5\:\text{cm}^3\text{/min}[/tex]
Find [tex]\frac{dr}{dt}[/tex] when diameter D = 20 cm.
We know that the volume of a sphere is given by
[tex]V = \dfrac{4\pi}{3}r^3[/tex]
Taking the time derivative of V, we get
[tex]\dfrac{dV}{dt} = 4\pi r^2\dfrac{dr}{dt} = 4\pi\left(\dfrac{D}{2}\right)^2\dfrac{dr}{dt} = \pi D^2\dfrac{dr}{dt}[/tex]
Solving for [tex]\frac{dr}{dt}[/tex], we get
[tex]\dfrac{dr}{dt} = \left(\dfrac{1}{\pi D^2}\right)\dfrac{dV}{dt} = \dfrac{1}{\pi(20\:\text{cm}^2)}(5\:\text{cm}^3\text{/min})[/tex]
[tex]\:\:\:\:\:\:\:= 0.08\:\text{cm/min}[/tex]
Which of the following methods of sampling is an example of a stratified random sample?
A. Randomly choosing a name from a list of names in the population and then choosing every tenth name thereafter.
B. From 500 names of members of a population in a hat drawing 50 names from the hat without looking.
C. Dividing a target population of students by grade level and choosing the first 25 names from each group.
D. Dividing a population of adults into males and females and randomly choosing a sample proportional to the numbers in each group.
Answer: D
Step-by-step explanation:
Answer: D
Step-by-step explanation:
Billy jogs 4/5 kilometer every minute.How many kilometers does he jog after 6 1/8 minutes
5.4 km
0.8×6
0.8×0.75
4.8+0.6 =5.4
4/5 of a kilometer = 800m
6 1/8 minutes = 49/8 min
Now
800×49/8
= 100×49
= 4900m
= 4.9km
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Factorize p2-15q-5p+2pq
Hope it's help you!!!!!!
On a map, the scale shown is 1 inch : 5 miles. If an island is 2.5 squire inches on the map, what is the actual area of the island? The actual island's area is square miles.
Answer:
62.5 square miles
Step-by-step explanation:
if the scale is 1 in. = 5 mi, then 1 square in. = 25 square miles
so if 1 in^2 = 25 mi^2
then you make a proportion
25/1 = x/2.5
(the square inches on the bottom and the square miles on top)
solving for x gives you
x=62.5 square miles
