Class 0-10 10-20 20-30 30-40 40-50 Frequency 5 $x$ 15 16 6 The missing frequency marked $\displaystyle x$ of the above distribution whose mean is 27 is :

Using the direct mean method, the sum of the products of class marks and frequencies is (5*5 + 15*x + 25*15 + 35*16 + 45*6) = 15x + 1430. The total frequency is 5 + x + 15 + 16 + 6 = 42 + x, and the given mean is 27. Setting up the equation 27 = (15x + 1430) / (42 + x) and cross-multiplying yields 1134 + 27x = 15x + 1430. Solving 12x = 296 gives x = 8.

• Thanks
• Wrong explanation