[tex]\large\underline{\sf{Solution-}}[/tex]
The frequency distribution table is
[tex]\begin{gathered} \begin{array}{|c|c|} \bf{Class \: Interval} & \bf{Frequency} \\ \\ 0 - 10 & 7 \\ \\10 - 20 & 9 \\ \\20 - 30 & 12 \\ \\30 - 40 & 16 \\ \\40 - 50 & x \\ \\50 - 60 & 6 \\ \\60 - 70 & 11 \end{array}\end{gathered} \\ [/tex]
Given that,
[tex]\rm \: Mode = 38 \\ [/tex]
[tex]\bf\implies \:Modal \: class \: = \: 30 - 40 \\ [/tex]
[tex]\rm \: f_0 = 12 \\ [/tex]
[tex]\rm \: f_1 = 16 \\ [/tex]
[tex]\rm \: f_2 = x \\ [/tex]
[tex]\rm \: h \: = \: 10 \\ [/tex]
[tex]\rm \: l \: = \: 30 \\ \\ [/tex]
We know, Mode for a continuous series is given by
[tex] \red{\boxed{ \boxed{\sf{Mode \: = \: l \: + \: \bigg(\dfrac{f_1 \: - \: f_0}{2f_1 \: - \: f_0 \: - \: f_2} \bigg) \: \times \: h }}}} \\ [/tex]
where,
l is lower limit of modal class.
[tex] \sf{f_1} [/tex] is frequency of modal class
[tex] \sf{f_0} [/tex] is frequency of class preceding modal class
[tex] \sf{f_2} [/tex] is frequency of class succeeding modal class
h is class height.
So, on substituting the values in above formula, we get
[tex]\rm \: \: 38= 30 + \bigg[\dfrac{16 - 12}{2 \times 16 - 12 - x} \bigg] \times 10\\[/tex]
[tex]\rm \: \: 38 - 30 = \bigg[\dfrac{4}{32 - 12 - x} \bigg] \times 10\\[/tex]
[tex]\rm \: \: 8 = \bigg[\dfrac{4}{20 - x} \bigg] \times 10\\[/tex]
[tex]\rm \: \: 2 = \bigg[\dfrac{1}{20 - x} \bigg] \times 10\\[/tex]
[tex]\rm \: \: 1 = \bigg[\dfrac{1}{20 - x} \bigg] \times 5\\[/tex]
[tex]\rm \: 20 - x = 5 \\ [/tex]
[tex]\rm \: - x = 5 - 20\\ [/tex]
[tex]\rm \: - x = - 15 \\ [/tex]
[tex]\bf\implies \:x = 15 \\ \\ [/tex]
[tex]\rule{190pt}{2pt} \\ [/tex]
Additional Information :-
1. Mean using Direct Method
[tex]\boxed{ \rm{ \:Mean = \dfrac{ \sum f_i x_i}{ \sum f_i} \: }} \\ \\ [/tex]
2. Mean using Short Cut Method
[tex]\boxed{ \rm{ \:Mean =A + \dfrac{ \sum f_i d_i}{ \sum f_i} \: }} \\ \\ [/tex]
3. Mean using Step Deviation Method
[tex]\boxed{ \rm{ \:Mean =A + \dfrac{ \sum f_i u_i}{ \sum f_i} \times h \: }} \\ \\ [/tex]