Breadcrumb Home > Videos > Add Using Mental Math Cite Add Using Mental Math In this video, Alex learns how to add 3-digit numbers uses mental math to add hundreds. TrendingHere are the facts and trivia that people are buzzing about. January 2021 Current Events: US News The Holocaust (1933–1945) Chinese New Year History, Meaning, and Celebrations Noble Titles and Ranks in a Monarchy The 5 Best Air Purifiers of 2020 Inaugural Trivia