To find the missing percentage, we can set up the equation based on the information given:
Let \( x \) be the percentage we are trying to find. The equation can be set up as follows:
\[ \frac{x}{100} \times 900 = 810 \]
Now, solve for \( x \):
- Multiply both sides by 100:
\[ x \times 900 = 81000 \]
- Divide both sides by 900:
\[ x = \frac{81000}{900} \]
- Calculate \( \frac{81000}{900} \):
\[ x = 90 \]
Thus, the missing percentage is \( 90% \).