Question

14. Вычислите 3, (7) + 6, (2). 80 A) 9, (9) B) C) 10 9
15. (98-11-3) Вычислите A) 1, 1 D) 0,8(3) - 0,4(6) 0, (3) C) 3 B) 12 89 9 D) 0,3​

Answer 1

Ответ:

$\bold{14.}\ C);\ \bold{15.}\ A)$

Пошаговое объяснение:

14.

$x = 3{,}(7);\\\\10x = 37{,}(7);\\\\10x - x = 37{,}(7) - 3{,}(7);\\\\9x = 34;\\\\x = \displaystyle\frac{{34}}{9}.\\[1.5em]y = 6{,}(2);\\\\10y = 62{,}(2);\\\\10y - y = 62{,}(2) - 6{,}(2);\\\\9y = 56;\\\\y = \displaystyle\frac{{56}}{9}.$

Тогда

$x + y = \displaystyle\frac{{34}}{9} + \displaystyle\frac{{56}}{9} = \displaystyle\frac{{90}}{9} = 10.$

На самом деле, ответ А) тоже правильный, т. к.

$9{,}(9)=10.$

15.

$x = 0{,}8(3);\\\\10x = 8{,}(3);\\\\10x - x = 8{,}(3) - 0{,}8(3);\\\\9x = 7{,}5;\\\\x = \displaystyle\frac{{75}}{{90}} = \displaystyle\frac{5}{6}.$

$2x = 1{,}6(6),$ поэтому

$0{,}4(6) = 1{,}6(6) - 1{,}2 = \displaystyle\frac{5}{3} - \displaystyle\frac{6}{5} = \displaystyle\frac{7}{{15}}.$

Тогда значение данного выражения равно

$\displaystyle\frac{{\displaystyle\frac{5}{6} - \displaystyle\frac{7}{{15}}}}{{\displaystyle\frac{1}{3}}} = \displaystyle\frac{{11}}{{30}}:\displaystyle\frac{1}{3} = \displaystyle\frac{{11}}{{30}} \cdot \displaystyle\frac{3}{1} = \displaystyle\frac{{11}}{{10}} = 1{,}1.$