Short artishock fixed by while(getchar()...)

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
//why line 47 get duplicated? how to fix it?
//fixed it by using while(ch=getchar)!='q'
//how to fix it, if i use scanf for symbol?

int main()
{
     char ch;
     float a,b,c,temp;//
     a = b = c = temp = 0.0;

     printf("artishoks a\t\nbeetroot b\t");
     printf("carrots c\t\nquit q\n");

     while( (ch=getchar())!='q' )
     {
        switch(ch)
        {
        case 'a':
            {
                printf("How much of artishoks do you want?\n");
                scanf("%f",&temp);
                a+=temp;
            }
            break;
        case 'b':
            {
                printf("How much of beetroot do you want?\n");
                scanf("%f",&temp);
                b+=temp;
            }
            break;
        case 'c':
            {
                printf("How much of carrots do you want?\n");
                scanf("%f",&temp);
                c+=temp;
            }
            break;

        }//end of switch
        printf("chose a,b,c,or q now\n");
        while(getchar()!='\n')
            continue;

        //scanf("%c",&ch);

     }//end of while

     return 0;
}