Hi. Is it true that when you redefine a variable using the same name, the new redefinition of the variable is not valid?

For example, in this code, where I'm trying to output the lowest number of change needed for an user input (example: if the user inputs .26, I need to output 2 [one quarter, one penny]).

Code:
#include <cs50.h>
#include<stdio.h>

int main(void)
{
    // get an input from user
    printf("How much change?: ");
    float change = GetFloat();

    int Change = round(change * 100);

    // how many quarters are needed
    while (Change >= 25)
    {
        quarters = (Change / 25);
        Change = (Change%25);
        // HERE IS MY QUESTION! I want to make Change (on the left) be Change%25 (on the right).  In the next while loop (to count dimes), is the (Change >= 10) using my new definition of Change (which is Change%25)?
    }  
    // how many dimes are needed 
    while (Change >=10)
    {
        dimes = (Change / 10);
        Change = (Change%10);
     }
    // there's more code concerning how many nickels and pennies are needed, but I deleted that to be concise in this question

    return 0;
}
Thank you!