1. **Problem:** 81 is 73% of what number? 2. **Formula:** To find the base number when given a part and a percentage, use the formula: $$\text{Base} = \frac{\text{Part}}{\text{Rate}}$$ where Rate is the percentage expressed as a decimal. 3. **Step 1:** Convert 73% to decimal: $$73\% = \frac{73}{100} = 0.73$$ 4. **Step 2:** Substitute the values into the formula: $$\text{Base} = \frac{81}{0.73}$$ 5. **Step 3:** Simplify the fraction: $$\text{Base} = \frac{81}{0.73} = 110.9589...$$ 6. **Step 4:** Round to a reasonable number of decimal places (usually 2): $$\text{Base} \approx 110.96$$ **Answer:** 81 is 73% of approximately 110.96.