Multiple choice general knowledge math & puzzles (1/10)18-(1/10)20=? 0.9 99/1020 99/10 none of these Reveal answer Fill a bubble to check yourself B Correct answer Explanation Assuming the notation means (1/10)^18 - (1/10)^20: Factor out (1/10)^18 to get (1/10)^18[1 - (1/10)^2] = (1/10)^18[1 - 1/100] = (1/10)^18(99/100) = 99/10^20 = 99/1020. This uses exponent factoring.