Fifteen topics, from lockers to charts.

A row of numbered lockers. Things sitting side by side, each with a number on its door.

Letters on a bead necklace. Words are rows of letters. Count them, flip them, match them.

Finding a page in a book. Sorted things let you jump to the middle and throw half away.

A chocolate bar of squares. Rows and columns, like a board game or a chocolate bar.

A toy train. Cars hooked one to the next. You only see the next car.

A pile of plates and a lunch line. Last in comes out first in a pile. First in comes out first in a line.

A row of light switches. Every number is a row of switches that are on or off.

A family tree. Each parent has at most two children, a left one and a right one.

A guessing game tree. Smaller things go left, bigger things go right. Every time.

A line where the smallest kid is always first. A tree that always keeps the smallest (or biggest) thing on top.

Grabbing the best candy first. Take the best looking choice now, and never look back.

Exploring a maze and walking back. Try a choice, go deeper, and step back when you hit a wall.

A tree of letters. Words that start the same share the same branch.

Towns and roads. Dots joined by lines. Any dot can connect to any other.

Writing answers on a chart so you never redo homework. Solve small versions once, write them down, build the big answer.