Câu 10: Tính bằng cách thuận tiện nhất
a. 
0,75 × 20/100 
+ 0,2 × 5,25 + 1/5 
× 4 b. 10 : 8 × 6,9 – 1,25 × 5,9
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a: \(0,75\cdot\dfrac{20}{100}+0,2\cdot5,25+\dfrac{1}{4}\cdot4\)
\(=0,75\cdot0,2+0,2\cdot5,25+0,25\cdot4\)
\(=0,2\left(5,25+0,75\right)+1\)
\(=6\cdot0,2+1=1,2+1=2,2\)
b: \(10:8\cdot6,9-1,25\cdot5,9\)
\(=1,25\cdot6,9-1,25\cdot5,9\)
\(=1,25\left(6,9-5,9\right)=1,25\cdot1=1,25\)