Question

Method: Exponential Model Q=Qoe^kt
How long does it take $1125 to triple if it is invested at 7% interest, compounded quarterly?

Answer 1

3 years

Answer 2

j

Answer 3

wrong.. the answer is 15.8 years... but when I do it I get 15.6y.. dont know why...

Answer 4

what is o?

Answer 5

Qo is initial quantity... in this case 1125

Answer 6

did you add the 2 at the end like you do when it does more than dobel

Answer 7

what is your k?

Answer 8

No, what i dont know how to do is the "quarterly compunded thing" i dont know how to place it in the equation...

Answer 9

@nincompoop k=0.07

Answer 10

what is your k?

Answer 11

do you know how to solve for t?

Answer 12

kinda... this is my work:

3(1125) = 1125e^0.07t
ln3 = lne^0.07t
1.0986 = 0.07t
15.67 = t

But the correct answer is supposed to be 15.8years... there is something wrong that I cant see... and it has to do with the quarterly compound part, but I dont know how to palce that on the equation.

Answer 13

where did you get 3 from?

Answer 14

3(1125) = 1125e^0.07t
3375 = 1125e^0.07t
divide by 1125 both side...

3 = e^0.07t

Answer 15

@Hero @ganeshie8 @wio @Luigi0210 @beccaboo333 @eliassaab does any of u guys know exponential model problems? pls I need to understand this for my math test tomorrow :)

Answer 16

there might be a problem with the equation

Answer 17

no the equation is right... I know where the problem is at.. I jsut dont know how to place it in the equation....

the problem says that the 7% compounds quaterly, (4) ... I jsut dont know how to place that 4 because everywhere I do it just gets wrong... idk if I have to use the Half life formula or what.. :(

Answer 18

@nincompoop

Answer 19

http://www.wolframalpha.com/input/?i=3+%3D++%281%2B0.07%2F4%29%5E%284t%29

Answer 20

hehe I deleted it, ganeshie

Answer 21

I told him that the equation is wrong, but he said it's correct so

Answer 22

e = continuous

but QUARTERLY is ur compounding - so formula changes

Answer 23

mmm.. @nincompoop im sorry for not trusting u i just cant make sense of it
i still dont get it tho :/

Answer 24

why 1+?

Answer 25

there are two compounding formulas
one is continuous, which makes use of e
and the other is by terms like annually, biannually, quarterly, monthly, which is the one ganeshie used

Answer 26

Use t = 4*3 = 12 (quarters as compounds quarterly) and 7/4% (quarterly rate) and see where that gets you!!

Then try the rate as r = [(1+7%)*(1/4)] - 1 to further refine if you are still not bang on.

Answer 27

it requires a proof why 1+ ... but all you need to know for now is when to use one over the other

Answer 28

so what would be the equation for it? like the formula.... Q=Qo1+K^t ? @nincompoop

Answer 29

@nincompoop done thx u soo much :) the best