Delhi Police Constable Exam Model Paper 1

Number of entries = 30
Wrong average = 106
Wrong entries = 92 and 186
Right entries = 82 and 136
Formula used:
Average = (Sum of entries)/Number of entries
Calculation:
Wrong total = 30 × 106 = 3180
⇒ Correct total = 3180 – 92 – 186 + 82 + 136 = 3120
∴ Correct average marks = 3120/30 = 104
Smart TrickNew average = Old average + (Error/Total numbers)
∴ New average = 106 + [(82 + 136) - (92 + 186)]/30 = 106 - (60/30) = 106 - 2 = 104.