Interactive resource
Multiplying Decimals with a Tenths Grid
Arithmetic. A 10×10 grid for 0.a × 0.b — purple overlap cells are hundredths in the product. Free interactive GeoGebra resource — adjust parameters in the…
Overview
Decimal multiplication is more than moving the point. The area model shows why the product counts hundredths.
Explanation
Split the unit square into a 10×10 hundredths grid.
0.a takes a columns and 0.b takes b rows; purple overlap has a×b hundredths, so the product is (a×b)/100.
This links place value to the meaning of decimal multiplication.
How to use
- Open the decimal-model scene.
- Adjust both tenths factors.
- Count purple cells.
- Match the product readout.
Example
0.3 × 0.4 → 12 hundredths → 0.12.
Knowledge points
FAQ
Can this extend to hundredths × hundredths?
Same idea with a finer grid for smaller place values.
Is this tool free?
Yes. It runs in the browser with no install.
Good for class demos?
Yes — project it and ask what changes when you drag a parameter.
How do I write the formula afterward?
Open the equation editor or symbol sheet and copy a clean expression.