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Webster 1828 Edition

ppr.

of sum. Adding together.

summing

summing ‎(plural summings)

The act or result of addition; a sum.
- 1815, John Dougall, The Young Man's Best Companion and Guide to Useful Knowledge
  In this manner each page [of accounts] is summed up, and […] the amount of the last page of all, as comprehending all the particular summings of the preceding pages, is to be considered as the total amount of the whole account.