While loop (Reforesting problem)

[cooltee13]

Hi guys, this is the other half of my assignment. ( I think im pretty much done with this one, I just cant figure out 1 thing) Sorry if Im not allowed to post 2 topics at once, I looked at the forum rules and couldn't find anything saying it was against the rules.

Anyways, with this program, 2 things are happening..1st, Im getting some huge numbers when It runs the program.

second, the black debugger box isnt staying open while I run the program. It exits before I can see the numbers. (it worked once, and thats why I saw the huge numbers..but hasnt worked since).

If someone could maybe modify a line or two to make it work, or tell me what I did wrong so I can try to fix it that would be good. Id prefer if you didn't rewrite the whole program.

#include <stdio.h>

#include <stdlib.h>

#include <math.h>

#include <iostream>

int main()

{

/* Declare and initialize variables. */

int year=1 ;

double Acres = 14000, uncut = 2500, Regrowth_rate = .02;

double reforest = 0;

while(year<=20)

{

reforest = uncut *(1+Regrowth_rate); // calculate growth

uncut = uncut + reforest ; // add that to uncut

cout << year << "\t" << reforest << endl;

year++;

printf ("%d %lf\n", year, reforest);

}

[Doli]

what calculations are you trying to do?

[cooltee13]

  Doli said:

what calculations are you trying to do?

Sorry I should have put that up there first. My mistake.

A problem in timber management is to determine how much of an area to leave uncut so that the harvested

area is reforested in a certain period of time. It is assumed that reforestation takes place

at a known rate per year, depending on climate and soil conditions. A reforestation

equation expresseses this growth as a function of the amount of timber standing and the

reforestation rate. For example, if 100 acrea are left standing after harvesting and the

reforestation rate is 0.05, then 100 + 0.05 x 100, or 105 acrees, will be forest at the end of

the first year. At the end of the second year, the number of acres of forest will be 105 +

0.05 x 105, or 110.25 acres.

1)

Assume that there are 14,000 acres total with 2,500 acres uncut and that the

reforestation rate is 0.02. Print a table showing the number of acres reforested at

the end of each year, for a total of 20 years.

[The Teej]

This is gonna sound weird, but initialise the values at 0 and then change them appropriately. Not sure if this will work, but add in a "break;" after the do-while.

Also, I assume you know you have a closing bracket missing at the end of your code, right (the one that closes the main method)?

EDIT: Think I know your problem...

/* your old code */
reforest = uncut *(1+Regrowth_rate); // calculate growth
uncut = uncut + reforest; // add that to uncut

/* my replacement code */
reforest = (uncut * Regrowth_rate) + uncut; // calculate growth
uncut += reforest;

Try this.

Edited April 8, 2008 by The Tjalian

[Doli]

  cooltee13 said:

Sorry I should have put that up there first. My mistake.

A problem in timber management is to determine how much of an area to leave uncut so that the harvested

area is reforested in a certain period of time. It is assumed that reforestation takes place

at a known rate per year, depending on climate and soil conditions. A reforestation

equation expresseses this growth as a function of the amount of timber standing and the

reforestation rate. For example, if 100 acrea are left standing after harvesting and the

reforestation rate is 0.05, then 100 + 0.05 x 100, or 105 acrees, will be forest at the end of

the first year. At the end of the second year, the number of acres of forest will be 105 +

0.05 x 105, or 110.25 acres.

1)

Assume that there are 14,000 acres total with 2,500 acres uncut and that the

reforestation rate is 0.02. Print a table showing the number of acres reforested at

the end of each year, for a total of 20 years.

Your calculations in the while loop are wrong. If you tried the example :

  Quote

For example, if 100 acrea are left standing after harvesting and the

reforestation rate is 0.05, then 100 + 0.05 x 100, or 105 acrees, will be forest at the end of

the first year. At the end of the second year, the number of acres of forest will be 105 +

0.05 x 105, or 110.25 acres.

in your program you would not get the same answer so you would know that its wrong. Plan it out on paper first.

hint: result = "acres left standing" + "reforestation rate" X "acres left standing"

[cykosis]

int main()

{

/* Declare and initialize variables. */

int year=1 ;

double Acres = 14000, uncut = 2500, Regrowth_rate = .02;

double reforest = 0;

while(year<=20)

{

uncut = uncut + (uncut*Regrowth_rate); // calculate growth

cout << year << "\t" << uncut << endl;

year++;

}

return 0;

}

This will give you 3714.87 after 20 years assuming a 2% regrowth.

You were essentially redundantly adding to your uncut value and unnecessarily complicating things it seemed.

[cooltee13]

  cykosis said:

int main()

{

/* Declare and initialize variables. */

int year=1 ;

double Acres = 14000, uncut = 2500, Regrowth_rate = .02;

double reforest = 0;

while(year<=20)

{

uncut = uncut + (uncut*Regrowth_rate); // calculate growth

cout << year << "\t" << uncut << endl;

year++;

}

return 0;

}

This will give you 3714.87 after 20 years assuming a 2% regrowth.

You were essentially redundantly adding to your uncut value and unnecessarily complicating things it seemed.

Ahh ok, ya I see what I did now, thanks for the help. Much appreciated.