Multiple choice general knowledge (1/10)18 - (1/10)20 = ? 99/1020 99/10 0.9 None of these Reveal answer Fill a bubble to check yourself A Correct answer Explanation Factor out (1/10)^18: (1/10)^18(1 - (1/10)^2) = (1/10)^18(1 - 1/100) = (1/10)^18(99/100) = 99/(10^18 * 10^2) = 99/10^20. This uses exponent rules and factoring.