Explanation
Here,
Expenditure of 4 members =Rs. 2800
So, expenditure of 1 member =28004=Rs. 700
Therefore,
Expenditure of 3 members =700×3=Rs. 2100
{\textbf{Step -1: Stating the arithmetic mean of n general numbers.}}
{\text{Let there be }}n{\text{ numbers }}{a_1}{\text{,}}{a_2}{\text{,}}{a_3}.....{a_n}{\text{. }}
{\text{Arithmetic mean of the numbers = }}\dfrac{{{a_1} + {a_2} + {a_3}{\text{ + }}.....{\text{ + }}{a_n}{\text{.}}}}{n}
{\textbf{Step -2: Finding arithmetic mean of 2 and 8.}}
{\text{Here we have only two numbers - }}2,8
{\text{Arithematic mean }}A = \dfrac{{2 + 8}}{2} = \dfrac{{10}}{2} = 5
{\textbf{Hence, }}\ {\textbf{Arithematic mean of 8 annd 2 is 5.}}
Let total work be W, and work done by 1 man in 1 day be w, then
5\times w\times 12=W
Also,
x\times w\times 10=W ( where x is number of men required to build the wall in 10 days)
Equating both equations, we get,x\times w\times 10=5\times w\times 12
\Rightarrow x\quad = \dfrac { 60 }{ 10 } =6\quad men
12 workers can complete a piece of work in 10 days
I/3 rd of original No's of workers = 12*1/3 = 4 workers
No of workers reduced then more no days are required
12*10÷ 4 = 30
Ans = 30 days
hence 20 days more
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