To find out how long it takes Rosa to decorate 1 cookie, we can start by determining her rate of decorating cookies.
If Rosa can decorate 6 cookies in 24 minutes, we can divide the total time by the number of cookies to find the time taken for each cookie:
\[ \text{Time per cookie} = \frac{\text{Total time}}{\text{Number of cookies}} = \frac{24 \text{ minutes}}{6 \text{ cookies}} = 4 \text{ minutes per cookie} \]
Therefore, it takes Rosa 4 minutes to decorate 1 cookie.