149 BPM
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4/4 ×2
Drag rhythmic values into up to 8 beat blocks per line to build a drum groove, or click a tile then click a block to place it — handy on a trackpad.
Math skill: Count Hands With Exactly One Special Card
How the beat teaches it: Every slot gives a small deck split into special and ordinary cards, and a hand size — count the hands with exactly one special card using C(special,1)×C(ordinary, rest). Build that many notes anywhere in the kit.
This is lesson 20 of 24 in RockBlocks Math, Probability, a free course where every lesson turns a math idea into something you can count, hear, and play. The previous lesson, “The Law of Total Probability,” covered compute a Weighted Total Across a Partition. Next is Lesson 21, “The Complement in Combinatorial Probability.”
Every slot above (A, B, C, D) is its own question, and it’s a real, blank RockBlocks beat the whole time — the same drag-and-drop tiles, kit, tempo, sheet music, and drummer view as anywhere else on the site. Tap ❓ Questionin the corner to read the current slot’s problem, build your answer right in the grid, then tap ✓ Check Answerto grade it. Once you’re done, keep going: expand the beat, drop it into a Stack, or save a copy to your own page — nothing here overwrites the lesson itself, so every visitor still starts from the same blank slots.