What is the difference between 100 and 45?

To find the difference between two numbers, you subtract the smaller number from the larger number. In this case, you need to subtract 45 from 100.

Doing the calculation:

100 - 45 = 55.

This result shows that the difference between 100 and 45 is indeed 55, which corresponds to the choice given. Understanding this operation—subtraction—is fundamental in mathematics, as it allows for comparing quantities and determining how far apart numbers are from one another. Recognizing that the correct answer reflects the result of the subtraction will aid in accurately solving similar problems in the future.