Looking for a mathematical formula

[tech291083]

Hi,

Lately I have been doing some numeracy tests in order to prepare myself for a test based interview as it seems to be the case with some of the firms hiring these days. Here is the question. I can not get my head around it. In fact I can get the answer doing it manually, but I think there a mathematical formula available to work this kind of problems out. Thanks a lot.

A town with a population of 2000 grows at a rate of 30% per annum. What will be its population in the next 4 years?

[swerdna]

Hi,

Lately I have been doing some numeracy tests in order to prepare myself for a test based interview as it seems to be the case with some of the firms hiring these days. Here is the question. I can not get my head around it. In fact I can get the answer doing it manually, but I think there a mathematical formula available to work this kind of problems out. Thanks a lot.

A town with a population of 2000 grows at a rate of 30% per annum. What will be its population in the next 4 years?

If P(t) is the population at time t, and if t is measured in years from year t0, then:
P(t>t0) = P(t0)exp**[0.3*(t-t0)]

Is that correct?

Swerdna

[Roxoff]

What you need is a straightforward compound interest formula. Have you taken a look on Wikipedia for help here?

[swerdna]

What you need is a straightforward compound interest formula. Have you taken a look on Wikipedia for help here?

Hi Roxoff. I see the compound interest formulae on your reference. I was using the population-growth formula with growth parameter set to 0.3 per 365 days. Why would bank interest be more relevant?

Swerdna

[fingal]

Must be a boring place to live, if the population increases at just 30% each year ...

Roughly 4400?

[daacosta]

Hi,

Lately I have been doing some numeracy tests in order to prepare myself for a test based interview as it seems to be the case with some of the firms hiring these days. Here is the question. I can not get my head around it. In fact I can get the answer doing it manually, but I think there a mathematical formula available to work this kind of problems out. Thanks a lot.

A town with a population of 2000 grows at a rate of 30% per annum. What will be its population in the next 4 years?

Is this a homework?

[Roxoff]

Hi Roxoff. I see the compound interest formulae on your reference. I was using the population-growth formula with growth parameter set to 0.3 per 365 days. Why would bank interest be more relevant?

Swerdna

lol, I think you're overcomplicating it somewhat. It's a simple algorithm.

Value N grows by X% per year over Y years...

In pseudocode:

  int value = N
  const rate = X
  const years = Y

  for (i = 1 to years)
     value = value+((value*rate)/100)
  next i

  return value

As you're looking at a timescale measured in years, you dont need to worry about numbers of days.

[likwid]

What kind of job are you talking?

[the bassinvader]

Roxoff is 100% correct. This is just a matter of a simple compound interest formula!!!

Why would bank interest be more relevant?

???. Banks aren't the only people that use this type of formula!!!!

[Roxoff]

Roxoff is 100% correct.

And now, 100% smug.