Đáp án:
$\begin{array}{l}
a)3.\sqrt {25} - 3.\sqrt {\dfrac{1}{9}} \\
= 3.5 - 3.\dfrac{1}{3}\\
= 15 - 1 = 14\\
b) - 4.\sqrt {\dfrac{4}{{25}}} + 3.\sqrt {0,16} - 2.\sqrt {0,04} \\
= - 4.\dfrac{2}{5} + 3.\sqrt {\dfrac{4}{{25}}} - 2.\sqrt {\dfrac{1}{{25}}} \\
= - \dfrac{8}{5} + 3.\dfrac{2}{5} - 2.\dfrac{1}{5}\\
= \dfrac{{ - 8 + 6 - 2}}{5}\\
= \dfrac{{ - 4}}{5}\\
c)\sqrt {\dfrac{1}{9}} .\sqrt {0,81} + \sqrt {0,09} \\
= \sqrt {{{\left( {\dfrac{1}{3}} \right)}^2}} .\sqrt {{{\left( {0,9} \right)}^2}} + \sqrt {0,{3^2}} \\
= \dfrac{1}{3}.0,9 + 0,3\\
= 0,3 + 0,3\\
= 0,6\\
d)\dfrac{2}{5}.\sqrt {16} + 2.\sqrt {\dfrac{{16}}{{25}}} :2\sqrt {\dfrac{1}{{16}}} \\
= \dfrac{2}{5}.4 + 2.\dfrac{4}{5}:\left( {2.\dfrac{1}{4}} \right)\\
= \dfrac{8}{5} + \dfrac{8}{5}:\dfrac{1}{2}\\
= \dfrac{8}{5} + \dfrac{8}{5}.2\\
= \dfrac{8}{5}.3 = \dfrac{{24}}{5}
\end{array}$
