In Week 24, we listed the Common Core Standards for Mathematical Practices. The last standard is Look for and express regularity in repeated reasoning.
Mathematically proficient students notice if calculations are repeated, and look both for general methods and for shortcuts. As they work to solve a problem, mathematically proficient students maintain oversight of the process, while attending to the details. They continually evaluate the reasonableness of their intermediate results. Ask your student if they have developed a shortcut to doing some of the problems and ask them to explain it to you.