a: \(3:2\frac17+1,5\cdot0,4\)
\(=3:\frac{15}{7}+0,6\)
\(=3\cdot\frac{7}{15}+0,6=\frac{21}{15}+0,6=1,4+0,6=2\)
Ta có: \(0,38-\left(5,97-0,12\right)+7,97\)
=0,38-5,97+0,12+7,97
=0,5+2
=2,5
Do đó: \(A=\frac{2}{2,5}=0,8\)
=>15% của A là: \(0,8\cdot0,15=0,12\)
b: \(1,95:\frac12-20\%\cdot\frac54+\frac74\cdot\frac15\)
\(=1,95\cdot2-0,2\cdot1,25+\frac{7}{20}\)
=3,9-0,25+0,35
=3,9+0,1
=4
\(1\frac17:0,8-\frac{5}{21}\cdot1,8\)
\(=\frac87:\frac{8}{10}-\frac{5}{21}\cdot\frac95\)
\(=\frac{10}{7}-\frac{9}{21}=\frac{10}{7}-\frac37=\frac77=1\)
Do đó: \(35\%\cdot B=\frac41=4\)
=>B=\(4:35\%=4:\frac{7}{20}=\frac{80}{7}\)
c: \(\frac{A}{B}=0.8:\frac{80}{7}=0,8\cdot\frac{7}{80}=\frac{5.6}{80}=0,07\)
