Thread: Hard stuck C Primer Plus example. Any help please :)

Hi guys new here ^.^ I'm working out some examples from C Primer Plus, Fifth Edition By Stephen Prata and I stumbled upon the following example.

I have managed to do simple and compound interest. But can't seem to do the last part. All help is appreciated.

John invests 200 dollars at 15% simple interest. (That is, every year, the investment earns an interest equal to 15% of the original investment.) Luke invests 200 dollars at 10% interest compounded annually. (That is, interest is 10% of the current balance, including previous addition of interest.) Write a program that finds how many years it takes for luke's invested sum to overtake John's along with a display showing the two values at that time.

Code:

#include<math.h>
int main()
{
        float p,q,r,SI,CI;
        int n;
       printf("Enter the value of Principal p = ");
        scanf("%f",&p);
        printf("Enter the value of Rate r = ");
        scanf("%f",&r);
        printf("Enter the value of Period in year n = ");
        scanf("%d",&n);
       SI = ((p*r*n)/100);
    printf("Simple Interest SI=%f \n",SI);
    q = 1+(r/100);
    CI=p*pow(q,n)-p;
       printf("Compound Interest CI=%f \n",CI);
    return 0;       
}

Thanks

What is the input for?
All numbers should be constants according to the exercise.
Only the number of years should be variable.

Code:

#include

Code:

<stdio.h>
#include<math.h>
int main()
{
    const float p = 200;
const float r =0.15;
const float g =0.1;
float q;
float SI;
float CI;
int n;

printf("Enter the value of Period in year n = ");
scanf("%d",&n);


SI = ((p*r*n)/100);
printf("Simple Interest SI=%f \n",SI);

q = 1+(g/100);
CI=p*pow(q,n)-p;
printf("Compound Interest CI=%f \n",CI);
return 0;
}

Here is what I ended up with after taking your advice. But it isn't running :/
Salem could you please tell me how and were i should make use of the loop function.
THanks

Hi salem thanks again, yes i know how to use a loop etc I just cant seem to understand how to use loops here in this case.

So how should it be then please? And regarding the coding is it right?
Thanks

Maybe like this:

Code:

double value_john = 200, value_luke = 200;
int years = 0;
do
{
   // calculate interest for luke and add to value_luke
   // add interest for john to value_john
   // note that interest for john is always the same so can be const
   // years++
}while (value_john >= value_luke);

After 9 years luke should have more money than john

Originally Posted by OldGuy2

Code:

   // calculate interest for luke and add to value_luke
   // add interest for john to value_john
   // note that interest for john is always the same so can be const
   // years++
}while (value_john >= value_luke);

I did it exactly like that. The names and amounts have changed in version six of book.

Code:

int main(void) {
  const float original = 100.0f;
  float daphne;
  float deirdre = daphne = original;
  int year = 0;