Question

qual dever ser o capital aplicado a uma taxa de juros simples de 25% a . a. para que em 6 meses renda R$425,00 de juros?

Answer 1

Olá,

Vamos lá,

Dados:
c=capital= ?
i= taxa= 25% a.a.= 25/100= 0,25
n=t=tempo= 6 meses = 0,5 ano 
j=juros= 425,00
Regime de Juros Simples

j=cit
425=c*0,25*0,5
425=0,125c
c = 425/0,125
c = 3.400,00

Resposta: R$ 3.400,00

Answer 2

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

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