How can i fix this

[shaunalejo]

#include <iostream>
#include <iomanip>
using namespace std;
int main()
{
double volume;
int cnt = 0 ;

cout<<"Please enter volume: ";
cin>>volume;

cout << fixed <<setprecision(2) ;
for( double concen = 100.0 ; concen > 50.0 ; concen=(volume * concen ) / (volume + 5))
{

cout << ++cnt << ". concentration " << concen << "% volume: " << volume << '\n' ;
}
system("pause");
}


the output is like this

1 Concentration: 90.00% Volume: 50 ml
2 Concentration: 81.00% Volume: 50 ml
3 Concentration: 72.90% Volume: 50 ml
4 Concentration: 65.61% Volume: 50 ml
5 Concentration: 59.05% Volume: 50 ml
6 Concentration: 53.14% Volume: 50 ml
7 Concentration: 47.83% Volume: 50 ml

my problem is how can i make it like this
8 Concentration: 47.83% Volume: 45 ml
9 Concentration: 47.83% Volume: 40 ml
10 Concentration: 47.83% Volume: 35 ml
11 Concentration: 47.83% Volume: 30 ml
12 Concentration: 47.83% Volume: 25 ml
13 Concentration: 47.83% Volume: 20 ml
14 Concentration: 47.83% Volume: 15 ml
15 Concentration: 47.83% Volume: 10 ml
16 Concentration: 47.83% Volume: 5 ml
17 Concentration: 47.83% Volume: 0 ml
Tessa can shampoo 8 times before stopping to water it down.

after concentration hitting 50 volume will be subtracted by 5 then it will displays what number concentration hits 50

thank you

[Dy7SLyTq]

1) use [ code ] [/ code] tags.
2) plz describe your problem more clearly (dont make us look for it)
3) don't use system in real world applications

[ar2007]

this is what you should serve, but did not mathematical correspondence. In brief is a imposition valid only for your request.
ciao

#include <iostream>
#include <iomanip>
using namespace std;
int main()
{
    int cnt = 0;
    double k; // this is volume value
    
    cout<<"Please enter volume: ";
    cin>>k;
    double z = k/(k+5);
    cout << fixed <<setprecision(2) ;
    for( double concen = 100.0; k>0; concen>50 ? (concen = z * concen):( k-=5))
    {
        cout << ++cnt << ". concentration " << concen << "% volume: " << k << '\n' ;
    }
    return 0;
}

Please enter volume: 50
1. concentration 100.00% volume: 50.00
2. concentration 90.91% volume: 50.00
3. concentration 82.64% volume: 50.00
4. concentration 75.13% volume: 50.00
5. concentration 68.30% volume: 50.00
6. concentration 62.09% volume: 50.00
7. concentration 56.45% volume: 50.00
8. concentration 51.32% volume: 50.00
9. concentration 46.65% volume: 50.00
10. concentration 46.65% volume: 45.00
11. concentration 46.65% volume: 40.00
12. concentration 46.65% volume: 35.00
13. concentration 46.65% volume: 30.00
14. concentration 46.65% volume: 25.00
15. concentration 46.65% volume: 20.00
16. concentration 46.65% volume: 15.00
17. concentration 46.65% volume: 10.00
18. concentration 46.65% volume: 5.00

ps-the values ​​that you make, do not correspond to the results of your formula, because in your post, you used approximations wrong.

[shaunalejo]

THX if fix the problem but how can i make the volume 0? also how can i limit the volume input by only divisible by 5?

THANK YOU

[ar2007]

can you be more
clear?

have these results mean?

Please enter volume: 
0. concentration 100.00% volume: 50.00
1. concentration 90.91% volume: 50.00
2. concentration 82.64% volume: 50.00
3. concentration 75.13% volume: 50.00
4. concentration 68.30% volume: 50.00
5. concentration 62.09% volume: 50.00
6. concentration 56.45% volume: 50.00
7. concentration 51.32% volume: 50.00
8. concentration 46.65% volume: 50.00
9. concentration 46.65% volume: 40.00
10. concentration 46.65% volume: 32.00
11. concentration 46.65% volume: 25.60
12. concentration 46.65% volume: 20.48
13. concentration 46.65% volume: 16.38
14. concentration 46.65% volume: 13.11
15. concentration 46.65% volume: 10.49
16. concentration 46.65% volume: 8.39
17. concentration 46.65% volume: 6.71
18. concentration 46.65% volume: 5.37
19. concentration 46.65% volume: 4.29
20. concentration 46.65% volume: 3.44
21. concentration 46.65% volume: 2.75
22. concentration 46.65% volume: 2.20
23. concentration 46.65% volume: 1.76
24. concentration 46.65% volume: 1.41
25. concentration 46.65% volume: 1.13
26. concentration 46.65% volume: 0.90
27. concentration 46.65% volume: 0.72
28. concentration 46.65% volume: 0.58
29. concentration 46.65% volume: 0.46
30. concentration 46.65% volume: 0.37
31. concentration 46.65% volume: 0.30
32. concentration 46.65% volume: 0.24
33. concentration 46.65% volume: 0.19
34. concentration 46.65% volume: 0.15
35. concentration 46.65% volume: 0.12
36. concentration 46.65% volume: 0.10
37. concentration 46.65% volume: 0.08
38. concentration 46.65% volume: 0.06
39. concentration 46.65% volume: 0.05
40. concentration 46.65% volume: 0.04
41. concentration 46.65% volume: 0.03
42. concentration 46.65% volume: 0.03
43. concentration 46.65% volume: 0.02
44. concentration 46.65% volume: 0.02
45. concentration 46.65% volume: 0.01
46. concentration 46.65% volume: 0.01
47. concentration 46.65% volume: 0.01
48. concentration 46.65% volume: 0.01
49. concentration 46.65% volume: 0.01
50. concentration 46.65% volume: 0.00
51. concentration 46.65% volume: 0.00
52. concentration 46.65% volume: 0.00
53. concentration 46.65% volume: 0.00
54. concentration 46.65% volume: 0.00
55. concentration 46.65% volume: 0.00

or are looking for a quantity of volume which leaves unchanged the concentration?