立方等于18的数是多少？

在数学中，立方是指一个数的三次方。换句话说，立方等于将一个数乘以自身两次。所以“立方等于18的数是多少？”可以转化为一个求解方程的问题。

设该数为x，则我们可以写出方程 x^3 = 18。

为了求解这个方程，我们首先需要了解立方根的概念。立方根就是一个数的立方等于它本身的根。在本例中，我们需要找到一个数的立方根等于18。

通过试错法，我们可以发现2的立方（2^3）等于8，而3的立方（3^3）等于27。因此，我们可以确定答案在2和3之间。

我们可以逐步尝试更接近18的数。如果我们选择2.5，那么2.5的立方等于15.625，显然小于18。如果我们选择2.7，那么2.7的立方等于19.683，显然大于18。

继续试错，如果我们选择2.6，那么2.6的立方等于17.576，接近18但仍然小于18。这意味着答案更接近2.7。

通过不断细化范围，我们可以逼近正确答案。经过几次尝试，我们最终可以得出结论：立方等于18的数约为2.64（具体为2.639）。

English translation:

What is the number whose cube is equal to 18?

In mathematics, a cube refers to the third power of a number. In other words, a cube is obtained by multiplying a number by itself twice. So, the question "What is the number whose cube is equal to 18?" can be transformed into solving an equation.

Let's assume the number is x, then we can write the equation as x^3 = 18.

To solve this equation, we first need to understand the concept of cube root. A cube root is a number that, when raised to the power of 3, equals the original number. In this case, we need to find a number whose cube root is equal to 18.

By trial and error, we can observe that the cube of 2 (2^3) is 8, while the cube of 3 (3^3) is 27. Therefore, we can determine that the answer lies between 2 and 3.

We can gradually try numbers closer to 18. If we choose 2.5, the cube of 2.5 is 15.625, which is obviously less than 18. If we choose 2.7, the cube of 2.7 is 19.683, which is obviously greater than 18.

Continuing with the trial and error approach, if we choose 2.6, the cube of 2.6 is 17.576, which is close to 18 but still less than 18. This means that the answer is closer to 2.7.

By narrowing down the range through several attempts, we can approach the correct answer. After a few trials, we can conclude that the number whose cube is approximately equal to 18 is 2.64 (specifically 2.639).