There are 15 years was his money invested.
Simple Interest is an easy method of calculating the interest for a loan/principal amount.
Given
Frank invests $1,000 in simple interest investment account that pays 8% a year.
After a number of years, he withdraws his balance of $2,200.
The number of years was his money inversted is;
[tex]\rm I= P\times r \times t[/tex]
Where p is the principal amount, r is the rate of interest, I is the amount and t is the time.
Substitute all the values in the formula;
[tex]\rm I= P\times r \times t\\\\2200-1000= 1000 \times .08 \times t\\\\1200 = 80t\\\\t = \dfrac{1200}{80}\\\\t=15[/tex]
Hence, in the 15 years was his money invested.
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