Explanation:

- We are given that the difference between 73% and 45% of a certain number is 112.

- Let's express this mathematically: \(0.73x - 0.45x = 112\).

- Simplifying the equation, we get: \(0.28x = 112\).

- To find the number \(x\), divide both sides by 0.28: \(x = \frac{112}{0.28}\).

- Calculating this gives: \(x = 400\).

- Option 1: 450 - If 73% and 45% calculations give a difference of 112, this would be incorrect.

- Option 2: 400 - When calculating, the difference equals exactly 112, so this is the right number.

- Option 3: 500 - The percentage difference here does not equal 112.

- Option 4: 550 - Likewise, does not fit the condition.

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