College Math Placement Practice Test

Finding a common denominator is the correct method for adding mixed numbers like 5 1/2 and 3 9/10 because it ensures that the fractional parts of the mixed numbers can be combined accurately.

To add fractions, they must have the same denominator. In this case, the denominators are 2 (from 1/2) and 10 (from 9/10). The least common denominator (LCD) for these fractions is 10.

Once the fractions are expressed with a common denominator, the next step is to convert each mixed number into a compatible form. For example, you would convert 5 1/2 into an equivalent fraction that has a denominator of 10, which is 5 5/10. Similarly, 3 9/10 is already expressed with the common denominator. At this point, you can add the whole numbers and the fractions separately to arrive at the final sum.

Using whole numbers directly could lead to inaccurate results since it ignores the fractional components that need to be added together. Subtracting first, then adding does not apply to this situation, as the question requires addition from the start. Converting to decimals is an alternative method, but not the standard approach for