These are practice problems, not a sample test. Your time on this is not restricted, and the problem set is over twice as long as the real test. These problems have already appeared as homework questions, but in this assignment the numerical values will likely be different. This assignment is optional and does not count in your grade.
So watch for this WebAssignment which will appear in your list of current WebAssignments starting Monday. This practice assignment will close on March 15, prior to the end of the test window which is March 18.