Ratio, proportion and rates of changeKS3 / GCSE

Calculating simple interest

Calculate simple interest and the final total.

  • Simple interest uses the original principal every year.
  • Interest = principal × annual rate as a decimal × years.
  • Add the interest to the principal when the question asks for the total.

Example 1

is invested at simple interest per year for years. Find the interest earned.

Simple interest is calculated on the original amount every year.

Example 2

is invested at simple interest per year for years. Find the total amount at the end.

Simple interest is calculated on the original amount every year.

Your turn

Question 1

is invested at simple interest per year for years. Find the interest earned.

Check answer
Simple interest is calculated on the original amount every year.
Question 2

is invested at simple interest per year for years. Find the total amount at the end.

Check answer
Simple interest is calculated on the original amount every year.
Question 3

is invested at simple interest per year for years. Find the interest earned.

Check answer
Simple interest is calculated on the original amount every year.
Question 4

is invested at simple interest per year for years. Find the total amount at the end.

Check answer
Simple interest is calculated on the original amount every year.
Question 5

is invested at simple interest per year for years. Find the interest earned.

Check answer
Simple interest is calculated on the original amount every year.
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