Question
 In a school with 400 students, the average age of the
boys is 16 years and that of the girls is 12 years. If the average age of school is 14 years 9 months. Then find the number of boys in the school.Solution
Total number of students in school = 400 Let the average age of Boys be ‘x. Then the number of girls in school = 400-x According to the question, x × 16 + (400 - x) × 12 = 400 × 14+9/12 16x + 4800 - 12x = 400 × 59/4 4x + 4800 = 5900 4x = 1100 x = 275 Number of boys = 275
0.3Ì…2Ì… + 0.54Ì…8Ì… - 0.1Ì…9Ì… is equal to :
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