45 is 20 percent of what number?

To find the number, you can set up a proportion equation. Let x represent the unknown number. The proportion equation would be: 45/x = 20/100. Cross multiplying gives you 100 * 45 = 20 * x. Simplifying further, you get 4500 = 20x. Dividing both sides by 20, you find x = 225. Therefore, 45 is 20 percent of 225.