Video solusi : The ages of the male inhabitants of a village were recorded and the following frequency table was obtained Find the mean. Age (in years) Number of persons 0-5 12 5-10 18 10-20 16 20-30 19 30-40 14 40-50 11 50-60 4 60-80 3 Hints: the given table is an exclusive frequency table. The class marks, xi, are 2.5; 7.5; 15; 25; 35; 45; 55; 70. i.e. class mark of a class lower limit + upper limit