Question

Qual deve ser o capital aplicado a uma taxa de juro simples de 25% a.a para que em 6 meses venda R$425,00 de juro?

Answer 1

6 meses = 0,5 ano

J = C *i *n
425 = C * 0,25 * 0,5
0,125 C = 425
C = R$ 3.400,00

Answer 2

$\sf\large \boxed{\boxed{\tt J = C \cdot i \cdot t}}$

_______________________

$\sf \displaystyle 425\:=\:C\:\cdot 0,\:25\:\cdot \left(\frac{1}{2}\right)\\\\\\\sf \boxed{\star \sf \ {Troque \:os \:lados} }\\\\\\\sf C\cdot \:0.25\left(\frac{1}{2}\right)=425\\\\\\\sf C\frac{0.25}{2}=425\\\\\\\sf 2C\frac{0.25}{2}=425\cdot \:2\\\\\\\sf 0.25C=850\\\\\\\sf \frac{0.25C}{0.25}=\frac{850}{0.25}\\\\\\\\\large \to \boxeed{\boxed{\sf C=3400}}$