To determine what percentage of 90 is 100, we set up the problem as follows:

Let $x$ be the percentage we want to find. We can express this as:

$x\% \times 90 = 100$

To find $x$, we divide both sides by 90:

$x = \frac{100}{90} \times 100$

Calculating this:

$x = \frac{100}{90} \times 100 = \frac{1000}{9} \approx 111.11\%$

So, 100 is approximately 111.11% of 90.

Would you like further details or have any questions?

Here are some related questions to explore:

1. What is 150% of 80?
2. How do you calculate the percentage increase from 90 to 100?
3. What percentage of 150 is 75?
4. How do you find the percentage difference between two numbers?
5. What is the inverse operation of finding a percentage of a number?

Tip: To find how much one number is as a percentage of another, always divide the first number by the second and multiply by 100.