Illustrative Mathematics K–5 · Grade 3 · Unit 3 · Wrapping Up Addition and Subtraction within 1,000
Welcome to Treasure Cove, a harbor full of ships, shells, and gold! Count coins in the Counting House, load cargo at the dock, run the Supply Shop, round from Lighthouse Point, estimate from the Crow’s Nest, and plan two-step voyages. Then dig up the chest on Treasure Island. Each station matches lessons from class.
Each station deals 8 fresh problems (Treasure Island deals 10). A right answer on the first try earns 10 points. After a wrong answer, the game names the likely mistake and gives one more try for 5 points. On Treasure Island, each right answer drops a gold coin in the chest.
Hints use the pictures from class: base-ten blocks, open number lines with jumps, adding and subtracting by place in expanded form, the standard algorithm worked column by column, number lines for rounding, and tape diagrams for two-step stories. A used hint caps that problem at 5 points.
Leaving out a 0 for an empty place, counting tens as ones, trading a hundred without taking it away, forgetting a new ten or hundred, taking the smaller digit from the bigger one instead of regrouping, forgetting a jump, rounding to the wrong place or always down, forgetting that halfway rounds up, giving the exact answer when asked to estimate, and using the wrong operation in one step of a two-step story.
Every number stays within 1,000, and each place regroups at most once. Two-step stories may multiply equal groups within 10 × 10, as in Unit 1. Ferries, trails, shells, and coins all come in amounts that make sense.
Each station matches a chapter of the Learn page for this unit, which walks through the ideas step by step.
Classroom Supplies (Lesson 21) is an optional lesson, so there’s no station for it.