A number $x$ is increased by $110\%$, and the resulting value is $3570$.

Represent the increase as a percentage of the original number. Since increasing by $110\%$ means the final number is $210\%$ of the original ($100\% + 110\% = 210\%$), simply divide $3570$ by $2.1$.

Students often misinterpret 'increased by 110%' as 'is 110% of', which would lead to calculating $1.1x = 3570$ instead of $2.1x = 3570$.

This concept of 'percentage base' is identical to calculating Compound Interest where the principal is the base value. Always identify if the percentage is of the original value or the updated value.