Question

va rog mult dau si coroana si puncte​

Answer 1

11)

a)

Numărul 15a se divide cu 9 daca si numai daca suma cifrelor sale se imparte la 9 => suma cifrelor ∈ {9,18,27...}

a este cifră, a∈{0,1,2,....,9}

1+5+a = 9 => a = 9-6 => a = 3

15a = 153

$\bf \dfrac{x}{6}= \dfrac{153}{27}$

$\bf 27\cdotx = 153\cdot6$

$\bf 27x = 918$

$\bf x =\dfrac{918}{27}$

$\bf x =\dfrac{\not918}{\not27}$

$\boxed{\bf x =34}$

b)

2a - numar prim

a- este cifra => a∈ {0,1,2...,9}

dar 2a ≤ 25 => a = 3, 2a = 23 ( 23 numar prim mai mic decat 25)

$\bf \dfrac{3}{46}= \dfrac{x}{23}$

$\bf x\cdot46=3\cdot23$

$\bf 46x=69$

$\bf x=\dfrac{69}{46}$

$\bf x=\dfrac{\not69}{\not46}$

$\boxed{\bf x=\dfrac{3}{2}}$

f)

$\bf \dfrac{x}{\dfrac{1}{3}}=\dfrac{\dfrac{7}{9}}{\dfrac{8}{3} }$

$\bf \dfrac{x}{1}\cdot \dfrac{3}{1}=\dfrac{7}{9}}\cdot{\dfrac{3}{8} }$

$\bf 3x=\dfrac{7}{\not9}}\cdot{\dfrac{\not 3}{8} }$

$\bf 3x=\dfrac{7}{24}}$

$\bf 3x \cdot 24 = 7$

$\bf 72x = 7$

$\boxed{\bf x = \dfrac{7}{72} }$