3D Shape Reasoning 6 - Count the Hidden Cubes

💡Tips for Parents

▸ Why It Matters Every earlier puzzle in this series let your child eventually see and confirm every cube, at least once they knew where to look. This one is different in a fundamental way: it hides a cube completely, with no view, gap, or shadow that reveals it directly, so it can only be reasoned into existence using a rule about how the physical world works — cubes are solid objects, and solid objects cannot float. That one physical fact, applied carefully, is enough to guarantee a hidden cube exists even though your child can never actually see it in the drawing. This is the essence of real-world 3D reasoning: packing an oddly shaped suitcase, reading an X-ray for a bone hidden behind another one, or judging whether a stack of boxes in a garage is stable all depend on inferring what's physically necessary rather than what's visible, and this worksheet is the first place in the series where that inference becomes unavoidable rather than optional. ▸ Getting Started Teach the "gravity rule" explicitly, as a rule your child can name and reuse: "if a cube is missing from the front of a pile, but the picture shows a taller stack directly behind that gap, there must be a cube underneath the gap holding that taller stack up — because cubes can't float in mid-air." Walk through the first puzzle together, physically tracing with a finger from the tall visible column down to where the missing support must sit, so the logic feels like a chain of cause and effect rather than an abstract rule to memorize. ▸ If They Get Stuck Have your child sketch a simple top-down "floor plan" of the pile — just a grid of squares seen from above — and write the height of each column as a number inside its square, using the gravity rule to fill in any square they can't see directly. Adding up the numbers on that floor plan is far more reliable than staring at the 3D picture and guessing, because it turns an intuition into a checkable calculation. ▸ Praise Points When your child spots a required hidden cube without prompting, name the exact skill they used: "You just used the gravity rule all on your own — cubes need support underneath, so you knew one had to be there even without seeing it. That's exactly how real 3D reasoning works!"

🎯What This Worksheet Builds

This worksheet teaches the "gravity rule" of 3D reasoning: if a taller stack is visible behind a gap, a hidden cube must be supporting it from below, since cubes can't float.

👉Next Step

When your child applies the gravity rule confidently, move to iq-3d-cube-counting-07, an advanced set with more columns and taller piles that rewards writing down each column's height instead of relying on memory.