Prorating

from The Collaborative International Dictionary of English v.0.48
Prorate \Pro*rate"\, v. t. [imp. & p. p. {Prorated}; p. pr. &
   vb. n. {Prorating}.] [From L. pro rata (sc. parte) according
   to a certain part, in proportion.]
   To divide or distribute proportionally; to assess pro rata.
   [U.S.]
   [1913 Webster]
    

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