For the same length $L$: open pipe fundamental $= v/(2L)$, closed pipe fundamental $= v/(4L)$. Ratio = 2:1. Open pipe has all harmonics; closed pipe has only odd. If an open pipe is closed at one end: fundamental halves and even harmonics disappear. If the question asks "which pipe can produce note of frequency $f$" — check if $f$ is an allowed harmonic. For closed pipe, $f$ must be an odd multiple of $f_1$.