Maria has to spend 5 1/2 hours to finish her community
project. If she has already spent 2 3/4 hours, how many more hours does she need to finish her community project?
To find the number of hours Maria still needs to finish her project, subtract the hours she has already spent from the total number of hours needed:
5 1/2 hours - 2 3/4 hours = 5/2 - 11/4
In order to subtract 11/4 from 5/2, we need to have a common denominator. The least common denominator for 2 and 4 is 4. Converting 5/2 to have 4 as the denominator gives us 10/4.
10/4 - 11/4 = -1/4
Maria still needs to spend -1/4, or 0.25 hours, to finish her community project.