New in version 1.1.
Multiply duration pair by rational multiplier and try to preserve numerator:
abjad> from abjad.tools import durationtools
abjad> durationtools.multiply_duration_pair_and_try_to_preserve_numerator((9, 16), Fraction(2, 3))
(9, 24)
Intended for certain types of meter multiplication.
Return integer pair.
Changed in version 2.0: renamed durationtools.pair_multiply_constant_numerator() to durationtools.multiply_duration_pair_and_try_to_preserve_numerator().