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UkoKoshka [18]
3 years ago
14

The half-life of a radioactive substance is 12 days. After 11 days a sample of the substance has been reduced to a mass of 7 mg.

Mathematics
2 answers:
Sloan [31]3 years ago
8 0
There is 8mg in all and that’s the answer
8_murik_8 [283]3 years ago
3 0

Answer:

  • 13.21 grams
  • 84.6 days

Step-by-step explanation:

The mass (m) remaining will be a function of the initial mass (m0) and the time in days (t) according to the exponential decay formula ...

  m = m0(1/2)^(t/12)

a) You want to find m0 for m=7 and t=11. Put these numbers in the formula and solve for m0.

  7 = m0(1/2)^(11/12) = 0.529732×m0

  m0 = 7/0.529732 = 13.21 . . . . grams

The initial mass of the sample was 13.21 grams.

__

b) We can use the value of m0 we found to determine the number of days until 0.1 mg will remain:

  0.1 = 13.21(1/2)^(t/12)

Dividing by 13.21 and taking logs, we have ...

  log(0.1/13.21) = (t/12)log(1/2)

  t = 12·log(0.1/13.21)/log(1/2) = 84.55

There will be only 0.1 mg left after 84.6 days.

_____

<em>Comment on the calculations</em>

For the latter part of the problem, be sure to use the full-precision value of  m0. Do not round any results until the final answer. Alternatively, you could use 7 mg for m0 and add 11 days to the result you get.

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Step-by-step explanation:

To solve this problem you must apply the proccedure shown below:

1. You need to apply the Distributive property on the left member of the equation:

2(x + 3) = x + 10\\ 2x+6=x+10

2. Now, you must solve for x, as following:

2x-x=10-6\\ x=4


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2,776,714 rounded to the greatest place value is?How many zeros are in the rounded number?The estimated speed of light using a p
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Step-by-step explanation:

7 0
3 years ago
Help plzzz thank you !
VashaNatasha [74]

Answer:

a. Ameribank-$15,157.50

b. Capital Two-$4,646.25

Step-by-step explanation:

a. Tad's savings is $15,000, we calculate his total amount at the end of the year for each bank:

#Ameribank

A=P+I=P+PRT\\\\=15000+15000\times 0.0105\times 1\\\\=\$15,157.50

#Huffington( we use the effective rate to calculate the compound amount):

i_m=(1+i/m)^m-1\\\\=(1+0.0095/12)^[12}-1=0.009541\\\\A=P(1+i_m)^n\\\\=15000(1.009541)^1\\\\=\$15,143.12

#Sixth-Third, Take 1 yrs=52 weeks:

i_m=(1+i/m)^m-1\\\\=(1+0.01/52)^{52}-1=0.01005\\\\A=15000(1.01005)^1\\\\=\$15,150.74

#Hence, Ameribank is the best option as his money grows to $15,157.50 which is greater than all the remaining two options.

b. We use the compound interest formula A=P(1+r/n)^{nt} to determine which bank gives the best option:

#Capital Two. r=3.75%, n=12,t=4

A=P(1+r/n)^{nt}\\\\=4000(1+0.0375/12)^{12\times4}\\\\=\$4,646.25

#J.C Morgan, t=2, r=3.55% n=12

A=P(1+r/n)^{nt}\\\\=4000(1+0.0355/12)^{12\times 2}\\\\=\$4,293.87

#Silverman Slacks, n=12,t=3, r=3.65%

A=P(1+r/n)^{nt}\\\\=4000(1+0.0365/12)^{12\times3}\\\\=\$4,462.14

We compare the investment amounts after t years:

Capital>Silver>Morgan=4646.25>4462.14>4293.87

Hence, Capital two is the best option with an investment amount of $4,646.25

8 0
3 years ago
Read 2 more answers
You are working a part-time job working 20 hours a week. After a week you earn $312. How much do you earn hourly? Write an equat
Lubov Fominskaja [6]
Firstly figure out how much money you earn per one hour. This is 312$ divided by 20 is 16$/hour. Then write an equation which represents only hourly earnings: y = 16x. To answer the last question just enter the value for variable x = 15, and you will get money earned per one week.
8 0
3 years ago
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