My son has a book called Mental Math in Junior High. He particularly liked when the author said "there is no single "right" way to do a problem in your head. Several alternative methods may be equally practical and efficient. To develop flexibility in thinking about numbers and number relationships, students should learn to look for an recognize a variety of approaches to the same problem. During discussion, encourage students to share different strategies and talk about the advantages of each.
Quick mental math ability is required on some of games he plays so he has been willing to practice different methods to see which is faster for him. He much prefers doing mental math to having to write out math problems because he has dysgraphia.
