Question

Sabendo que um capital C,aplicado a juros simples,rende em 4 meses o equivalinte a 1/5 de seu valor,determine a taxa de juros mensal.

Answer 1

$J=\frac{1}{5}~de~C=\frac{1}{5}\cdot C=\frac{C}{5}\\\\C=C\\\\i=?\\\\t=4~meses$
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$J=C\cdot i\cdot t\\\\\\\dfrac{C}{5}=C\cdot i\cdot4\\\\\\\dfrac{1}{5}=4\cdot i\\\\\\i=\dfrac{1}{20}~ao~m\^es\\\\\\i=\dfrac{100\%}{20}~ao~m\^es\\\\\\\boxed{\boxed{i=5\%~ao~m\^es}}$