"100+4 1" represents the surface area of the whole earth because in this solution, it is assumed that the total area of the earth's oceans is 100, so the total area of the earth's land is 4 1, which is not rigorous. It is best to assume that the total area of the earth's oceans is y.

Because the final answer to this question is a ratio, that is, a percentage, the answer is the same whether the total ocean area of the earth is a real number like 100 or an unknown number y.