Lesson Notes By Weeks and Term v4 - JHS 2

Lesson Video

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Performance objectives

• Explain what powers of 10 are.
• Multiply whole numbers and decimals by powers of 10.
• Divide whole numbers and decimals by powers of 10.
• Apply these skills to real-life problems.

Lesson summary

This lesson focuses on a fundamental skill in mathematics: multiplying and dividing whole numbers and decimals by powers of 10 (like 10, 100, 1000). This is not just a classroom trick; it's a powerful shortcut used in everyday life. Whether we are calculating the cost of multiple items at the market, converting measurements like centimetres to metres, or understanding large numbers in science and finance, mastering this skill makes calculations faster and easier. For instance, if one bag of cement costs GH₵ 85, how much will 10 bags cost? This lesson will give us a quick way to find the answer without a long multiplication process.

Lesson notes

Concept 1: What are Powers of 10? Powers of 10 are numbers you get by multiplying 10 by itself a certain number of times. They are the foundation of our number system (the decimal system). 10¹ = 10 10² = 10 × 10 = 100 10³ = 10 × 10 × 10 = 1000 10⁴ = 10 × 10 × 10 × 10 = 10,000

Key Idea: The exponent (the small number at the top) tells you two things: How many times 10 is multiplied by itself. How many zeros follow the 1.

Concept 2: Multiplying by Powers of 10 When we multiply a number by a power of 10, we are making the number larger. Each digit in the number moves to a higher place value.

The Rule: To multiply a number by a power of 10 (10, 100, 1000...), we move the decimal point to the right. The number of places we move is equal to the number of zeros in the power of 10 (or the value of the exponent).