Multiple choice Which one number is wrong in the given series. 77, 94, 81, 92, 86, 90, 87, 88 81 92 90 86 Reveal answer Fill a bubble to check yourself D Correct answer Explanation The series alternates +17 and -13: 77(+17)94(-13)81(+17)98(-13)85... But 86 appears instead of 85, breaking the pattern. 86 is the wrong number.