I need help with this question

Answer:6.4

Step-by-step explanation: need to divide

6 0

2 years ago

he radioactive element carbon-14 has a half-life of 5750 years. A scientist determined that the bones from a mastodon had lost

elena-s [515]

Answer:

The bones were 12,485 years old at the time they were discovered.

Step-by-step explanation:

Amount of the element:

The amount of the element after t years is given by the following equation, considering the decay rate proportional to the amount present:

$A(t) = A(0)e^{-kt}$

In which A(0) is the initial amount and k is the decay rate, as a decimal.

The radioactive element carbon-14 has a half-life of 5750 years.

This means that $A(5750) = 0.5A(0)$ , and we use this to find k. So

$A(t) = A(0)e^{-kt}$

$0.5A(0) = A(0)e^{-5750k}$

$e^{-5750k} = 0.5$

$\ln{e^{-5750k}} = \ln{0.5}$

$-5750k = \ln{0.5}$

$k = -\frac{\ln{0.5}}{5750}$

$k = 0.00012054733$

So

$A(t) = A(0)e^{-0.00012054733t}$

A scientist determined that the bones from a mastodon had lost 77.8 % of their carbon-14. How old were the bones at the time they were discovered?

Had 100 - 77.8 = 22.2% remaining, so this is t for which:

$A(t) = 0.222A(0)$

Then

$0.222A(0) = A(0)e^{-0.00012054733t}$

$e^{-0.00012054733t} = 0.222$

$\ln{e^{-0.00012054733t}} = \ln{0.222}$

$-0.00012054733t = \ln{0.222}$

$t = -\frac{\ln{0.222}}{0.00012054733}$

$t = 12485$

The bones were 12,485 years old at the time they were discovered.

8 0

2 years ago

I think the answer is c can someone check me

Katen [24]

Answer:

D

Step-by-step explanation:

you first have to find the domain by finding where the expression is defined

so the answer would be x>5

6 0

3 years ago

Bill spent 70 on fertilizer and weed killer for his lawn .Each pound of fertilizer cost 50 cents and each once of weed killer co

meriva

An equation that correctly represent this relationship if x represents the number of pounds of fertilizer and y the number of ounces of weed killer is 0.5x + 3.5y = 70

<u>Solution:</u>

Given that, Bill spent 70 on fertilizer and weed killer for his lawn

Each pound of fertilizer cost 50 cents and each once of weed killer cost 3.50

We have to write an equation, if x represents the number of pounds of fertilizer and y the number of ounces of weed killer.

Now,<em> total amount = amount for fertilizers + amount for weed killers.</em>

Total amount = number of pounds of fertilizers x cost per pound + number of ounces of weed killer x cost per ounce.

$\begin{array}{l}{\rightarrow 70=x \times 0.50+y \times 3.50} \\\\ {\rightarrow 0.5 x+3.5 y=70}\end{array}$

Hence, the equation is 0.5x + 3.5y = 70

5 0

2 years ago

Julie has a jewlery box shaped like a cube. The volume of the jewlery box is v cubic inches. Write an

Stolb23 [73]

Answer: ∛v

Step-by-step explanation:

Since we know volume is measured height x width x length, we know the equation we'd use here would be:

___ x ___ x ___ = v in³

If this was area, we would have ___ x ___ = v in², and it would be easy to find each blank. You would just find the square root of "v", making your answer √v.

When you have 3 things multiplied by each other (that are exactly the same, which is the situation here since this is a cube), you will want to find ∛x (if x is our unknown variable). This means that we are finding ONE-THIRD of the number ... sort of. So if x was equal to 8, then ∛x = 2, because 2 x 2 x 2 = 8.

In our situation here, x = v, and since we don't know the actual number, we will keep it as a square root, so the answer to your question is ∛v.

I really hope I was able to explain easy enough, feel free to ask anything else!

7 0

3 years ago

I need help with this question​

I need help with this question