if a number p is prime , and 2 p + 3 = q , where q is also prime , then the decimal expansion of 1 / q will produce a decimal with q - 1 digits . if this method produces a decimal with 166 digits , what is the units digit of the product of p and q ?
"1 / 5 = 0.2 . . ( a repeating pattern one digit long ) a"
subtract(divide(subtract(add(166, 1), 3), 2), subtract(divide(subtract(add(166, 1), 3), 2), 1))