Compound Interest

Test yourself

Compound Interest

In summer, the number of ants in a colony increases by 20% each day. On the first day, there are 10,000 ants. How many are there after 3 days?

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Key terms

  • Compound interest is when the amount of interest for a bank account is calculated again each interval rather than just using the starting amount.
  • Depreciation is when the value of an item decreases each year as it ages.
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And again for the 3rd day

  • We can also solve these problems using the formula:
    • N = S × (multiplier)n

Jump to other topics


1.1Place Value

1.2Factors & Multiples


1.4Fractions, Decimals & Percentages

1.5Growth & Decay

1.6Measurements & Units



3Ratio, Proportion & Rates of Change

4Geometry & Measures



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