A number x is mistakenly divided by 10 instead of being multiplied by 10. what is the percentage error in the result?

Explanation:-

$$\eqalign{ & {\text{Actual}}\,{\text{result}} = 10x \cr & {\text{By}}\,{\text{mistake}}\,{\text{it}}\,{\text{has}}\,{\text{been}}\,{\text{divided}}\,{\text{by}} \cr & 10 = \frac{x}{{10}} \cr & \% \,{\text{change}} = \left[ {\frac{{10x - \left( {\frac{{10}}{x}} \right)}}{{10x}}} \right] \times 100 = 99 \cr & = - 99\% \cr & {\text{Since, actual value is greater than the wrong value}}{\text{.}} \cr & \cr & {\text{Alternatively,}} \cr & {\text{Let}},\,x = 10 \cr & {\text{Actual}}\,{\text{result}} = 10 \times 10 = 100 \cr & {\text{Wrong}}\,{\text{result}} = \frac{{10}}{{10}} = 1 \cr & {\text{Change}} = \left( {1 - 100} \right) = - 99 \cr & \% \,{\text{change}} = - 99\% \cr}$$