1. **State the problem:** Find the number for which 90 is 25%. 2. **Formula:** To find the base when given a part and a percentage, use the formula: $$\text{Base} = \frac{\text{Part}}{\text{Percentage as a decimal}}$$ 3. **Convert percentage to decimal:** 25% = $\frac{25}{100} = 0.25$ 4. **Apply the formula:** $$\text{Base} = \frac{90}{0.25}$$ 5. **Calculate:** $$\text{Base} = 360$$ 6. **Interpretation:** 90 is 25% of 360. **Final answer:** 360