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The starting amount is 100% of itself, so an increase uses a multiplier bigger than 1 and a decrease uses a multiplier smaller than 1. For example, a 6% increase uses 1.061.061.06, while a 6% decrease uses 0.940.940.94.
To build a multiplier, rewrite the new percentage as a decimal. So 8% increase means 108%=1.08108\% = 1.08108%=1.08, and 25% decrease means 75%=0.7575\% = 0.7575%=0.75. Compound interest and depreciation both use these multipliers again and again over time.
Question 1
4 marksSarah wants to invest £5000 for three years. She can choose between Bank P and Bank Q.
2.5% compound interest per annum
3% compound interest in the first year 2.2% compound interest for each extra year
Which bank will give Sarah the most interest after three years? You must show your working.
In percentage calculations, what is the multiplier for a 6% increase?
Revision notes for WJEC GCSE Maths Compound Interest and Depreciation: explanations and worked examples.
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A laptop loses 7%7\%7% of its value each year. Which multiplier is used to calculate its value after each year?