Question

Uma bolsa é vendida por R$42,00 seu preço fosse aumentado em 20%, quanto passaria a custar

Answer 1

$\Large\boxed{\begin{array}{l}\sf Um\,aumento \,de\,20\%\,equivale\,a\,multiplicar\\\sf o\,prec_{\!\!,}o\,por\,1,2.\\\underline{\rm prova:}\\\sf 20\%=\dfrac{20}{100}=0,2\\\sf aumento=1+20\%=1+0,2=1,2.\\\underline{\rm O\,novo\,prec_{\!\!,}o\,da\,bolsa\,ser\acute a:}\\\sf 1,2\cdot42=R\ 50,40\end{array}}$

$\large\boxed{\begin{array}{l}\underline{\rm Resoluc_{\!\!,}\tilde ao\,por\,regra\,de\,3\,simples:}\\\sf 42\longrightarrow 100\%\\\sf x\longrightarrow 20\%\\\sf 100x=20\cdot42\\\sf 100x=840\\\sf x=\dfrac{840}{100}\\\\\sf x=8,4.\\\sf O\,valor\,da\,bolsa\,ser\acute a\,42+8,4=R\ 50,40\end{array}}$