40 ARYABHATIYA 27. The denominators of multipliers and divisors are multi- plied together. Multiply numerators and denominators by the other denominators in order to reduce fractions to a common denominator. For the first part of the rule I have given what seems to be the most likely literal translation. The exact sense is uncertain. Kaye (agreeing with Rodet) translates, "The denominators are multiplied by one another in multiplication and division." If that is the correct translation the genitive plural is curious. Paramesvara explains gunakdra as gunagunyayor dhatir atra gunakdrasabdena vivaksitd. hdrya ity arthah and then seems to take bhdgahdra as referring to a fractional divisor of this product. Can the words bear that construction? In either case the inversion of numerator and denominator of the divisor would be taken for granted. It is tempting to take gunakdrabhdgahdra as mean- ing "fraction" and to translate, "The denominators of fractions are multiplied together." But for that interpretation I can find no authority. 28. Multipliers become divisors and divisors become multi- pliers, addition becomes subtraction and subtraction becomes addition in the inverse method. The inverse method consists in beginning at the end and working backward. As, for instance, in the question, "What number multiplied by 3, divided by 5, plus 6, minus 1, will give 5?" 29. If you know the results obtained by subtracting suc- cessively from a sum of quantities each one of these quantities set these results down separately. Add them all together and divide by the number of terms less one. The result will be the sum of all the quantities.