EX.—0·025 × 0·7 = 0·0175. The product is obtained with the slide projecting to the _left_, and the number of digits is therefore −1 + 0 = −1. EX.—0·000184 × 0·005 = 0·00000092. The sum of the number of digits in the two factors = −3 + (−2) = −5, but as the slide projects to the _right_, the number of digits will be −5 − 1 = −6. From the last two examples it will be seen that when the first significant figure of a decimal factor does not immediately follow the decimal point, the minus sign is to be prefixed to the number of digits, counting as many digits _minus_ as there are 0’s following the decimal point. Thus, 0·03 has −1 digit, 0·0035 has −2 digits, and so on. Some little care is necessary to ensure these minus values being correctly taken into account in determining the number of digits in the answer. For this reason many prefer to treat decimal factors as whole numbers, and to locate the decimal point according to the usual rules for the multiplication of decimals. Thus, in the last example we take 184 × 5 = 920, but as by the usual rule the product must contain 6 + 3 = 9 decimal places, we prefix six cyphers, obtaining 0·00000092. When both factors consist of integers as well as decimals, the number of digits in the product, and therefore the position of the decimal point, will be determined by the usual rule for whole numbers. Another method of determining the number of digits in a product deserves mention, which, not being dependent upon the position of the slide, is applicable to all calculating instruments. GENERAL RULE FOR NUMBER OF DIGITS IN A PRODUCT.—_When the first significant figure in the product is smaller than in_ EITHER _of the factors, the number of digits in the product is equal to the_ SUM _of the digits in the two factors. When the contrary is the case, the number of digits is 1_ LESS _than the sum of the digits in the two factors. When the first figures are the same, those following must be compared._