Indices & Standard Form

Overview

Year 9 consolidates indices and pushes standard form further. Students use the laws of indices with positive, negative and zero powers, and write both very large and very small numbers in standard form, including with negative powers of 10. This is the final Lower Secondary step before the IGCSE Number topic, where standard form and indices are used constantly.

What You Will Learn

• Use the laws of indices with positive, negative and zero indices
• Understand that a negative index means a reciprocal (e.g. 2⁻³ = 1/2³)
• Write large and small numbers in standard form A × 10ⁿ
• Convert between standard form and ordinary numbers, including small numbers
• Compare and order numbers written in standard form

Key Vocabulary

Common Mistakes to Avoid

• Thinking a negative index makes the number negative, rather than a reciprocal
• Using a positive power of 10 for a small number (it should be negative)
• Writing the front number A outside the range 1 ≤ A < 10
• Forgetting to apply the laws of indices to the numbers as well as the powers

Frequently Asked Questions