Question

Aflați cât la sută reprezintă numărul a din numărul b dacă :a/b=2 /5, a/6=b/25

Answer 1

Explicație pas cu pas:

a)            

$\bf \dfrac{a}{b} =\dfrac{2}{5}\Rightarrow 5\cdot a = 2\cdot b\Rightarrow \boxed{ \bf a = \dfrac{2b}{5} }$

$\text{\bf Aflam cat la suta reprezinta numarul ~a ~din ~b}$

$\bf a = \dfrac{a}{b} \cdot 100$

$\bf a = \dfrac{2b}{5}$

$\bf a= \dfrac{~\dfrac{2b}{5}~}{b} \cdot 100=\dfrac{2b}{5}:b \cdot 100=\dfrac{2\not b}{5}\cdot\dfrac{1}{\not b} \cdot 100=\dfrac{200}{5} =40\Rightarrow$

$\red{\boxed{\bf 40\% ~~reprezinta~~a~~din~ ~b}}$

==========pav38================

b)

$\bf \dfrac{a}{6} =\dfrac{b}{25}\Rightarrow 25\cdot a = 6\cdot b\Rightarrow \boxed{ \bf a = \dfrac{6b}{25} }$

$\text{\bf Aflam cat la suta reprezinta numarul ~a ~din ~b}$

$\bf a = \dfrac{a}{b} \cdot 100$

$\bf a = \dfrac{6b}{25}$              

$\bf a= \dfrac{~\dfrac{6b}{25}~}{b} \cdot 100=\dfrac{6b}{25}:b \cdot 100=\dfrac{6\not b}{25}\cdot\dfrac{1}{\not b} \cdot 100=\dfrac{600}{25} =24\Rightarrow$

$\purple{\boxed{\bf 24\% ~~reprezinta~~a~~din~ ~b}}$  

===========pav38===============

c)            

$\bf \dfrac{8}{b} =\dfrac{3}{a}\Rightarrow 8\cdot a = 3\cdot b\Rightarrow \boxed{ \bf a = \dfrac{3b}{8} }$

$\text{\bf Aflam cat la suta reprezinta numarul ~a ~din ~b}$

$\bf a = \dfrac{a}{b} \cdot 100$

$\bf a = \dfrac{3b}{8}$

$\bf a= \dfrac{~\dfrac{3b}{8}~}{b} \cdot 100=\dfrac{3b}{8}:b \cdot 100=\dfrac{3\not b}{8}\cdot\dfrac{1}{\not b} \cdot 100=\dfrac{300}{8}\Rightarrow$

$\pink{\boxed{\bf 37,5\% ~~reprezinta~~a~~din~ ~b}}$