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Year 10 - Maths

Changing compound interest rates

Percentages

Unit Summary

In this unit pupils will learn how to perform simple and compound interest calculations using percentages.

Lesson Summary

You will learn to carry out compound interest calculations where the percentage changes.

Key Notes

  • By considering the calculations for compound interest, you can be more efficient.
  • Through understanding the structure, you can adapt to changing percentages.
  • Part of that structure is understanding the period of time for each interest rate.
  • Part of that structure is understanding finding a percentage of a percentage.

Vocabulary To Learn

  • Compound interest: Compound interest is the interest calculated on the original amount and the interest accumulated over the previous period.
  • Exponential form: When a number is multiplied by itself multiple times, it can be written more simply in exponential form.

Common Mistakes To Avoid

  • Assuming that an increase of 10% followed by a decrease of 10% takes you back to 100%, etc.

3 Quick Questions (With Answers)

1. Solve this in steps: explain the method from this lesson and why each step matters.

By considering the calculations for compound interest, you can be more efficient. Through understanding the structure, you can adapt to changing percentages.

2. Use this key word in a maths sentence and explain it clearly. 'Compound interest'

Compound interest is the interest calculated on the original amount and the interest accumulated over the previous period. Use this word when showing your method, then check your final answer is reasonable.

3. Spot and fix this common maths mistake.

Mistake: Assuming that an increase of 10% followed by a decrease of 10% takes you back to 100%, etc. Correction: Provide plenty of examples to illustrate the structure of what happens. If you increase a number by a percentage the number will increase meaning that you will be finding 10% of a larger number and hence decrease by more.

More Lessons In This Unit

Browse all guides in the Year 10 Maths guide library.