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A certain population declines by 4% each year. What is the percentage decline each month? (Round your answer to two decimal places.)

 

An investment declines in value by 5% each month. By what percentage does its value decline in a year? (Round your answer to two decimal places.)

 Mar 25, 2020
 #1
avatar+1956 
+1

1) Since there are 12 months in a year... 

 

-4/12 will be -1/3% or -0.33 decrease each month

 Mar 25, 2020
 #3
avatar+115 
0

it was .34 sad

Shaezy  Mar 25, 2020
 #24
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0

THIS IS THE CORRECT ANSWER:

 

A - 1.04^(1/12) =1.00327373 - 1 x 100 =0.33 % - percntage decline per month.

 

B -1.05^12 =1.795856 - 1 x 100 =79.59% - percentage decline in 1 year.

Guest Mar 25, 2020
 #26
avatar+115 
0

They are both incorrect, the first one was .34 and the second one is incorrect. I have one more attempt. 

Shaezy  Mar 25, 2020
 #2
avatar+1956 
+1

2) There are 12 months in a year....

 

-5*12=-60.

 

It declines by 60% or 0.6 each year.

 Mar 25, 2020
 #5
avatar+115 
0

the 2nd part is also incorrect. These questions are over constant percentage change, so they use formulas like a=1+r for growth and a=1-r for decay. Im stressing out badly because they are super confusing. 

Shaezy  Mar 25, 2020
 #4
avatar+1956 
+1

0.34?! What?!!!!

 Mar 25, 2020
 #7
avatar+115 
0

you were close though. and I appreciate you taking the time to try and help me. 

Shaezy  Mar 25, 2020
 #6
avatar+1956 
+1

I'm confused too... I'm so sorry about my incorrect answers. I will look at them again right now!

 Mar 25, 2020
 #8
avatar+115 
0

no worries lol, I have a few more attempts on the others before they are completely wrong. 

Shaezy  Mar 25, 2020
 #9
avatar+1956 
+1

Okay. Don't trust me 100%, though. I'm a really rushed, angry elementary school kid... LOL!

 Mar 25, 2020
 #11
avatar+115 
0

An elementary school kid?? No way. 

Shaezy  Mar 25, 2020
 #10
avatar+1956 
+1

Is it (0.2)^12

 Mar 25, 2020
 #13
avatar+115 
0

that isn't it either lol. 

Shaezy  Mar 25, 2020
 #12
avatar+1956 
+1

Yes elementary school.... Really!!!!!!!!!! Anyway, is it correct?

 Mar 25, 2020
 #15
avatar+115 
0

that's amazing!!! When I was in elementary I didn't learn this. It was the basics of math. So kuddos!

Shaezy  Mar 25, 2020
 #29
avatar+41 
0

I see I'm not the only one who is in elementary school here, I'm in fifth grade. 

Zekken  Apr 3, 2020
 #14
avatar+1956 
+1

CPhill? Melody? GET IN HERE!!!!!
LOL

 Mar 25, 2020
 #16
avatar+115 
0

hahahaha

Shaezy  Mar 25, 2020
 #17
avatar+1956 
+1

LOL!

 

I got the answer for the other one you asked, though. It's 0.03

 Mar 25, 2020
 #18
avatar+115 
0

Is that one about the 25% question? Where you answered 0.03?

Shaezy  Mar 25, 2020
 #19
avatar+1956 
+1

Yep! Is it right?

CalTheGreat  Mar 25, 2020
 #21
avatar+115 
0

I haven't tried because I don't think it is correct and this is my last attempt. 

Shaezy  Mar 25, 2020
 #20
avatar+1956 
+1

Oh, wait! Geno's here!!!!!!!

 Mar 25, 2020
 #22
avatar+20883 
+1

One of the compound interest formula is:  F  =  A(1 + x )t

where  F  =  final amount

            A  =  initial amount

            x  =  interest rate, as a decimal

            t  =  number of years

For this problem, if the inital population = A, then the final population will be 0.96A (because it decreased by 4%).

So:                                                    0.96A  =  A(1 + x)12

Divide both sides by A:                       0.96  =  (1 + x)12

Find the 12th root of 0.96:    0.9966039468  =  1 + x

Subtract 1:                                                x  =  -0.003396                  (the '-' indicates that it is decreasing)

 Mar 25, 2020
 #28
avatar+115 
0

That would be correct because the answer was .34. Where were you sooner?! lol Im kidding, thank you though!!

Shaezy  Mar 25, 2020
 #23
avatar+1956 
+1

You haven't? Okay... makes sense. Try messaging CPhill or Melody.

 Mar 25, 2020
 #25
avatar+111321 
+1

An investment declines in value by 5% each month. By what percentage does its value decline in a year? (Round your answer to two decimal places.)

 

Let A  be   the value of the investment at the beginning  of the year

 

At the  end of the year, the investment will be worth 

 

A(.95)^12  ≈  .54036 A  

 

So......the %  decline in one year =  1 -.54036  ≈   45.964% ≈  45.96%

 

 

cool cool cool

 Mar 25, 2020
 #27
avatar+115 
0

Awesome, thank you! That is how we did it in class but I get confused when it asks for years and months. 

Shaezy  Mar 25, 2020

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