$N=N_0e^{kt}$ where N is the amount after decay, No is the initial amount, e is Euler's number, k is the decay constant, and t is the time in minutes. For us, the first equation looks like this:

$7=12e^{k(70)}$ and we will solve that for k and then use that value of k in the second equation to find time.

Begin by dividing 7 by 12 to get

$\frac{7}{12}=e^{k(70)}$ Now take the natural log of both sides since the natural log and that e are inverses. The e then disappears:

$ln(\frac{7}{12})=k(70)$

Plug the left side into your calculator and then set it equal to the right side, giving us:

$-.5389965007=70k$

Divide both sides by 70 to get the k value of

k = -.00769995

Now the second equation looks like this:

$2=12e^{(-.00769995)t$ where t is our only unknown now that we know k.

Begin by dividing both sides by 12 to get

$\frac{1}{6}=e^{-.00769995t$ and take the natural log of both sides again to eliminate the e:

$ln(\frac{1}{6})=-.00769995t$

Take care of the left side on your calculator to get

-1.791759469 = -.00769995t and divide both sides by -.00769995 to get

t = 232.697 minutes

4 0

2 years ago

The original price of a Shirt was $45. In sales, the shirt is reduced to $32.50. Calculate the percentage reduction.

Klio2033 [76]

Answer:

27.8%

Step-by-step explanation:

$\frac{32.5}{45} =0.722$

0.722 = 72.2%

The % reduction is:

(100-72.2)% = 27.8%

Hope this helps

8 0

2 years ago