To complete these number patterns mathematicians must determine by what number each is constantly increasing. However, this isn't your typical skip counting; scholars count by numbers like 18, 60, and even 101 to fill in the missing parts of each sequence. Some will complete these using all mental math while others may want to write out each addition equation (decide if this is something you will allow). These 18 patterns aren't numbered, so consider numbering them before copying to make review easier.