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tresset_1 [31]
3 years ago
11

a 40 gram sample of a substance that's used for drug research has a k-value of 0.1446. find the substance's half life in days

Mathematics
2 answers:
Dovator [93]3 years ago
4 0

Answer:

4.7935 days

Step-by-step explanation:

The expression that describes exponential decay is the following:

N(t) = No * e^{-kt}

Where N(t) is the mass of the substance after a period t of time.

No is the original amount of substance

k is the relative decay rate and t is the period of time elapsed.

The half life is the period of time after which the amount of substance has decreased by half.

We can issolate t in the expression, using the properties of logarithms:

\frac{N(t)}{No}=e^{-kt}

ln(\frac{N(t)}{No}) = -k*t

t = - ln(\frac{N(t)}{No})/k = - ln(\frac{1}{2})/0.1446 = 4.7935 days.

Novay_Z [31]3 years ago
3 0

The applicable decay formula is:N = No*e^(-kt)WhereN = Mass left after time tNo = Original massk = constantt = half lifeUsing the values given,N/No = e^(-0.1446t) = 1/2ln (1/2) = -0.1446 t *ln e^1-0.6931 = -0.1446 tt = 0.6331/0.1446 = 4.79 daysTherefore, half-life is 4.8 days.

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Can anyone help me plz ?? Lakita has 66 water bottles for the 5K race participants. In addition, she is planning to buy boxes of
Ivanshal [37]

Answer:

65,81,97,113,129


Step-by-step explanation:


she has 65 water bottles and she is buying boxes of water bottles (x) that hold 16 water bottles each. She can only buy up to 5 water bottles.



f(x) = 16x + 65...where f(x) = total water bottles and x = number of boxes


x < = 5 here is ur restriction



the range is ur f(x) values which represent the total number of water bottles...keep in mind, she can only buy 5. Therefore, the numbers that can be subbing in for x are 0 thru 5.



So when subbing in 0 thru 5 for x, the results for f(x) are :


{ 65,81,97,113,129 }

8 0
3 years ago
Another easy question pls answer​
timama [110]
Always true, 90+90=180
6 0
2 years ago
Read 2 more answers
Click on the measure that is equivalent to 5 meters.
dimaraw [331]

Answer:

500 cm

Step-by-step explanation:

100 cm is equal to 1 meter. *5 is 5 meters or 500 cm

Sorry if I'm wrong. I don't think I am but there is always a possibility

6 0
3 years ago
Read 2 more answers
For which system of equations is (5, 3) the solution? A. 3x – 2y = 9 3x + 2y = 14 B. x – y = –2 4x – 3y = 11 C. –2x – y = –13 x
Alla [95]
The <u>correct answer</u> is:

D) \left \{ {{2x-y=7} \atop {2x+7y=31}} \right..

Explanation:

We solve each system to find the correct answer.

<u>For A:</u>
\left \{ {{3x-2y=9} \atop {3x+2y=14}} \right.

Since we have the coefficients of both variables the same, we will use <u>elimination </u>to solve this.  

Since the coefficients of y are -2 and 2, we can add the equations to solve, since -2+2=0 and cancels the y variable:
\left \{ {{3x-2y=9} \atop {+(3x+2y=14)}} \right. &#10;\\&#10;\\6x=23

Next we divide both sides by 6:
6x/6 = 23/6
x = 23/6

This is <u>not the x-coordinate</u> of the answer we are looking for, so <u>A is not correct</u>.

<u>For B</u>:
\left \{ {{x-y=-2} \atop {4x-3y=11}} \right.

For this equation, it will be easier to isolate a variable and use <u>substitution</u>, since the coefficient of both x and y in the first equation is 1:
x-y=-2

Add y to both sides:
x-y+y=-2+y
x=-2+y

We now substitute this in place of x in the second equation:
4x-3y=11
4(-2+y)-3y=11

Using the distributive property, we have:
4(-2)+4(y)-3y=11
-8+4y-3y=11

Combining like terms, we have:
-8+y=11

Add 8 to each side:
-8+y+8=11+8
y=19

This is <u>not the y-coordinate</u> of the answer we're looking for, so <u>B is not correct</u>.

<u>For C</u>:
Since the coefficient of x in the second equation is 1, we will use <u>substitution</u> again.

x+2y=-11

To isolate x, subtract 2y from each side:
x+2y-2y=-11-2y
x=-11-2y

Now substitute this in place of x in the first equation:
-2x-y=-13
-2(-11-2y)-y=-13

Using the distributive property, we have:
-2(-11)-2(-2y)-y=-13
22+4y-y=-13

Combining like terms:
22+3y=-13

Subtract 22 from each side:
22+3y-22=-13-22
3y=-35

Divide both sides by 3:
3y/3 = -35/3
y = -35/3

This is <u>not the y-coordinate</u> of the answer we're looking for, so <u>C is not correct</u>.  

<u>For D</u>:
Since the coefficients of x are the same in each equation, we will use <u>elimination</u>.  We have 2x in each equation; to eliminate this, we will subtract, since 2x-2x=0:

\left \{ {{2x-y=7} \atop {-(2x+7y=31)}} \right. &#10;\\&#10;\\-8y=-24

Divide both sides by -8:
-8y/-8 = -24/-8
y=3

The y-coordinate is correct; next we check the x-coordinate  Substitute the value for y into the first equation:
2x-y=7
2x-3=7

Add 3 to each side:
2x-3+3=7+3
2x=10

Divide each side by 2:
2x/2=10/2
x=5

This gives us the x- and y-coordinate we need, so <u>D is the correct answer</u>.
7 0
3 years ago
Which number between 17/4and 20
Talja [164]
Answer : 4.485
I’m pretty sure I just went with someone else answer !
8 0
3 years ago
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