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We are asked to find the interest rate using simple interest. Therefore we would use the equation
\n$\\displaystyle r=\\frac{c_1-c_0}{c_0}$
\nwhere $r$ is the rate of return, $c_1$ is the final value of the investment and $c_0$ is the initial value of the investment.
\n\nIn our situation we have,
\n$\\displaystyle r=\\frac{\\var{c1}-\\var{c0}}{\\var{c0}}$
\n\nCalculating this we find
\n$\\begin{align}r&\\approx\\var{rdec}\\\\&=\\var{rrounded}\\%\\text{ (to 2 decimal places)}\\end{align}$
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\n\n[[0]] $\\%$ (to 2 decimal places)
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