The rules that use the vocabulary item "fifty" are:

<tens>

fifty

<tenminutes>

fifty

<scale_number-gapsout_null-gapsin_null>

two hundred fifty

two hundred and fifty

two fifty

three hundred fifty

four hundred fifty

five hundred fifty

six hundred fifty

seven hundred fifty

eight hundred fifty

nine hundred fifty

fifty thousand

fifty five thousand

one hundred fifty thousand

two hundred and fifty thousand

two hundred fifty thousand

three hundred fifty thousand

four hundred fifty thousand

five hundred fifty thousand

six hundred fifty thousand

seven hundred fifty thousand

eight hundred fifty thousand

nine hundred fifty thousand