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
Step -1: Stating the arithmetic mean of n general numbers.
Let there be n numbers a1,a2,a3.....an.
Arithmetic mean of the numbers = a1+a2+a3 + ..... + an.n
Step -2: Finding arithmetic mean of 2 and 8.
Here we have only two numbers - 2,8
Arithematic mean A=2+82=102=5
Hence, 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×w×12=W
Also,
x×w×10=W ( where x is number of men required to build the wall in 10 days)
Equating both equations, we get,x×w×10=5×w×12
⇒x=6010=6men
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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