Clavis usuræ [electronic resource] : or, a key to interest, both simple and compound: containing practical rules, plainly express'd in Words at length; whereby all the various Cases of Interest, and Annuities, or Leases, either in Possession, or Reversion, and Purchasing Free-Hold Estates, &c. may very easily be Resolv'd, both by the Pen and a small Table of Logarithms, hereunto annex'd; For all Rates of Interest, and Times of Payment whatsoever; Illustrated by Variety of Examples. To which is added, rules to be observ'd in estimating the value of annuities, or leases, and Insurances for Lives, &c. Also, The Business of Rebate or Discompt, and the Equation of Payments (very useful for Merchants and other Deallers) is here Rectified and truly Determin'd. By J. Ward, Author of the Young Mathematician's Guide, &c.