Question

Nr a reprezinta 20% din nr b. Cat la suta din nra reprezinta numarul b? Cat la suta reprezinta a din a+b/

Answer 1

$a = \frac{20}{100} \times b$

$a = \frac{2}{10} \times b$

$a = \frac{1}{5} \times b$

$a = \frac{b}{5}$

$\frac{x}{100} \times b = a$

$\frac{x}{100} \times b = \frac{b}{5}$

$\frac{bx}{100} = \frac{b}{5}$

$5bx = 100b \: | \div 5b$

$x = 20$

$\frac{y}{100} \times (a + b) = a$

$\frac{y(a + b)}{100} = a$

$y(a + b) = 100a$

$y = \frac{100a}{a + b}$

$y = \frac{100 \times \frac{b}{5} }{ \frac{b}{5} + b}$

$y = \frac{ \frac{100b}{5} }{ \frac{b}{5} + \frac{5b}{5} }$

$y = \frac{20b}{ \frac{b + 5b}{5} }$

$y = \frac{20b}{ \frac{6b}{5} }$

$y = 20b \times \frac{5}{6b}$

$y = \frac{100b}{6b}$

$y = \frac{50}{3}$

$y = 16.(6)$

$y = 16.66$