In a school with 400 students, the average of the age of

Solution

Let the average age of Boys be ‘x’ According to question, x × 16 + (400 - x) × 12 = 400 × 14(3/4) 16x + 4800 - 12x = 400 × 59/4 4x + 4800 = 5900 4x = 1100 x = 275 Number of girls = 400 - 275 = 125 Alternate Method: By Alligation, Boys                       Girls 16                            12              59/4 59/4 - 12          :      16 - (59/4) 11/4                 :           5/4 11                    :           5 So Number of girls = 5/(5+11) of 400 = 5/16 of 400 = 125