Usually there is no one right way to solve a mathematical problem; different methods have different advantages and disadvantages.
For Grades: 3-5
Learning Goal 2
In using mathematics, choices have to be made about what operations will give the best results. Results should always be judged by whether they make sense and are useful.
For Grades: 6-8
Learning Goal 2b
Using mathematics to solve a problem requires choosing what mathematics to use; probably making some simplifying assumptions, estimates, or approximations; doing computations; and then checking to see whether the answer makes sense.