With the use of formula, the interest rate is 18.2%
The Interest is the product of the principal, time and the rate in percentage. That is, I = PTR / 100
Where
Substitute all the parameters into the formula
80 = (880 x 0.5R)/100
cross multiply
8000 = 440R
R = 8000/440
R = 18.2%
Therefore, the (simple) interest rate is 18.2%
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