NTSE Stage 2 SAT 2018 Exam Question Paper

Since, the mean of a group of eleven consecutive natural numbers is m, then
$\frac{\mathit{x}+\mathit{x}+1+...+\mathit{x}+10}{11}=\mathit{m}$
$11\mathit{x}+55=11\mathit{m}$
$\mathit{x}+5=\mathit{m}$
$\mathit{x}=\mathit{m}-5$
Let n be the mean when next six consecutive natural numbers are included in the group then
$\frac{\mathit{x}+\mathit{x}+1+....+\mathit{x}+16}{17}=\mathit{n}$
$17\mathit{x}+\frac{16\times 17}{2}=17\mathit{n}$
$17\mathit{x}+8\times 17=17\mathit{n}$
Hence, required percentage change in the mean