Total number of students who are under study = Total number of persons in the age group of 15 years to 45 years, Number of persons from (15 – 20) + (20 – 25) + (25 – 30) + (30 – 35) + (35 – 40) + (40 - 45) = (450 + 250 + 150 + 100 + 75 + 50) = 1075 Number of persons under study in the age group 30 - 35 = 100 ⇒ Percentage of population under study which is in the age group of 30 - 35 = no. of persons in the age group 30 - 35/total no. of students who are under study × 100 = (100/1075) × 100 = 9.30%