Hot Dots Jr Let's Master Pre-K Math. These two-book sets include a Hot Dots Jr. Pen and 100 interactive lessons on a variety of math skills from place value and math facts to telling time and identifying money values. Two 50-page books and Hot Dots Jr Pen. Bonus 15 challenge activities that prepare children for next-level skills. Encourages independent learning. Pen requires 2 AAA batteries (not included). Ages 4+.