how much did you invest if you earned $131.60 in interest at a rate of 4% for seven years?

The amount invested is $ 470Solution:Given that ,  we have earned $131.60 as simple interest for an amount deposit at the rate of 4% for seven years. We have to find the amount invested.  That is, we need to find the principal sumLet us use the simple interest formulaThe simple interest is given as:[tex]\text { Simple interest }=\frac{p r i n c i p a l \times \text {rate of interest } \times \text {number of years}}{100}[/tex]Here, simple interest = $ 131.60Rate of interest = 4 %Number of years = 7principal = ?Substituting the values in formula, we get[tex]\begin{array}{l}{131.6=\frac{\text { principal } \times 4 \times 7}{100}} \\\\ {131.6 \times 100=\text { principal } \times 4 \times 7} \\\\ {13160=\text {principal } \times 28} \\\\ {\text {Principal }=470}\end{array}[/tex]Thus the amount invested is $ 470