1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Helen [10]
3 years ago
9

Substance A decomposes at a rate proportional to the amount of A present. ​a) Write an equation relating A to the amount left of

an initial amount Upper A 0 after time t. ​b) It is found that 18 lb of A will reduce to 9 lb in 4.2 hr. After how long will there be only 1 lb​ left?
Mathematics
1 answer:
horrorfan [7]3 years ago
7 0

Answer:

Step-by-step explanation:

a) The equation relating A to the amount left of an initial amount Upper A 0 after time t is

A(t) = A0e^(kt)

b) It is found that 18 lb of A will reduce to 9 lb in 4.2 hr. It means that

A0 = 18

A = 9

t = 4.2

Therefore, substituting into the formula, it becomes

9 = 18e^(4.2k)

9/18 = e^(4.2k)

0.5 = e^(4.2k)

Taking ln of both sides of the equation, it becomes

Ln0.5 = ln e^(4.2k)

- 0.693 = 4.2k

k = - 0.693/4.2

k = - 0.165

The equation becomes

A(t) = 18e^(- 0.165t)

For A = 1(1 lb left), then

1 = 18e^(- 0.165t)

1/18 = e^(- 0.165t)

0.056 = e^(- 0.165t)

Taking ln of both sides, it becomes

Ln0.056 = ln e^(- 0.165t)

- 2.88 = - 0.165t

t = - 2.88/-0.165

t = 17.5 hours

After 17.5 hours, 1 lb would be left

You might be interested in
Multiply or divide as indicated b^7/ b^6
shtirl [24]
<h3>♫ - - - - - - - - - - - - - - - ~Hello There!~ - - - - - - - - - - - - - - - ♫</h3>

➷ When values with exponents are divided, you should subtract the exponents.

7 - 6 = 1

Your answer should be b^1, which can also be written as just 'b'

<h3><u>✽</u></h3>

➶ Hope This Helps You!

➶ Good Luck (:

➶ Have A Great Day ^-^

↬ ʜᴀɴɴᴀʜ ♡

6 0
3 years ago
Read 2 more answers
#10
amm1812

Answer:

There are 3 green marbles in the box.

Step-by-step explanation:

15% = 0.15

To figure out how much 15% of 21 is, you must multipl the decimal form of the percentage by the whole number. This will give you how much of that number that percentage is.

0.15 * 21 = 3.15  

But you can't have 0.15 of a marble, so you must round as well.

3 green marbles in the box.

3 0
3 years ago
1.15 + m = 10 Please give an answer
garik1379 [7]

Answer:

M = 8.85

Step-by-step explanation:

10 - 1.15 = 8.85

8 0
2 years ago
While Hadley was looking through her math textbook she came across the words "inverse operations", but couldn't remember what th
egoroff_w [7]

Answer:

Inverse operations are opposite operations that undo each other. Addition and subtraction are inverse operations. Multiplication and division are inverse operations.




4 0
3 years ago
Write a positive or negative integer that represents the situation.
Pachacha [2.7K]

Answer:

what situation...there"s no any situation

8 0
2 years ago
Read 2 more answers
Other questions:
  • How are volatility and risk related in an investment?
    8·2 answers
  • A line has a slope of 3 and passes through
    13·1 answer
  • PLEASE HELP OR IM gonna FAILLLLLLLL!!!!!!!!
    12·1 answer
  • I need some help pls thx
    9·1 answer
  • 20 POINTS!!! HELP ASAP!! What are the domain and range of the function graphed below?
    9·1 answer
  • | 14
    5·1 answer
  • A drawer contains black socks and white socks. A person randomly selects two socks without replacement. The probability of selec
    7·1 answer
  • Find the surface area of q cylinder.
    8·1 answer
  • Sorry for asking alot i just need to get 10 out of 10
    5·1 answer
  • You toss a coin (heads or tails), then spin a three-color spinner (red, yellow, or blue). Complete the tree diagram, and then us
    7·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!