1.

If the mean of the following data is 59, find the missing frequency.Class 10-30 30-50 50-70 70-90 90-110Frequency 10 7 5 X 12​

Answer»

Step-by-step EXPLANATION:

Given:Mean of the following data is 59.

\begin{array}{|c|c|}\cline{1-2} Class& Frequency\\\cline{1-2} 10-30& 10\\\cline{1-2} 30-50& 7\\\cline{1-2} 50-70& 5\\\cline{1-2} 70-90& X\\\cline{1-2} 90-110& 12\\\cline{1-2}\end{array}

To find: X

Solution:

We KNOW that

Mean =  \frac{ \Sigma \: x_if_i}{ \Sigma \: f_i}  \\

Find class mark for each class and put the VALUES in the formula,in order to find X

\begin{array}{|c|c|c|c|}\cline{1-4} Class& Frequency& x_i&x_if_i\\\cline{1-4} 10-30& 10&20&200\\\cline{1-4} 30-50& 7& 40&280\\\cline{1-4} 50-70& 5& 60&300\\\cline{1-4} 70-90& X& 80&80X\\\cline{1-4} 90-110& 12& 100&1200\\\cline{1-4}Total&34+X&&1980+80X\\\cline{1-4}\end{array}

Put the values

59 =  \frac{1980 + 80X}{34 + X} \\  \\ cross \: multiply \\  \\ 59(34 + X) = 1980 + 80X\\  \\ 59 \times 34 + 59X = 1980 + 80X \\  \\ 59X - 80X = 1980 -2006  \\  \\  - 21X = -26 \\  \\ 21X =26  \\  \\ X =1.24  \\  \\

Thus,

VALUE of missing frequency is 1.24

Which is not possible.

Frequency should be positive integer.

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