Multiplying Decimals by Multiples of Ten

MatholiaChannel

This instructional video demonstrates a clear, two-step strategy for multiplying decimal numbers by multiples of ten (specifically 30 and 50). The narrator guides viewers through two distinct examples: 16.7 x 30 and 2.83 x 50. The method involves decomposing the multiplier into its factors (e.g., changing 30 into 3 x 10), performing the single-digit multiplication first using a standard vertical algorithm, and finally adjusting the place value by multiplying by 10. The video explores key mathematical themes including the associative property of multiplication, standard vertical multiplication algorithms with decimals, and the effect of multiplying by powers of ten on decimal placement. Visual cues, such as yellow sticky notes for side calculations and animated arrows for decimal shifting, help reinforce the procedural steps. The content emphasizes decomposing larger numbers to simplify mental or written calculations. For educators, this video serves as an excellent model for teaching composite strategies in arithmetic. It moves beyond rote memorization by showing *why* the math works—breaking a complex problem into manageable parts. It is particularly useful for students transitioning from whole number multiplication to decimal operations, offering a reliable method that minimizes placement errors. Teachers can use this to introduce the topic or as a remediation tool for students struggling with decimal alignment.