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1) 2,75 - 5/6 × 2/5 = 2,75 - (5/6) × (2/5) = 2,75 - 1/3 = 2,75 - 0,33 = 2,42
2) 1,25 - (5/6 - 0,75) - 3/5 = 1,25 - (5/6 - 0,75) - 3/5 = 1,25 - (5/6 - 3/4) - 3/5 = 1,25 - (5/6 - 9/12) - 3/5 = 1,25 - (10/12 - 9/12) - 3/5 = 1,25 - 1/12 - 3/5 = 1,25 - 0,08 - 0,6 = 1,25 - 0,68 = 0,57
3) 4/9 × 0,75 + 8/5 + 3,125 = (4/9) × 0,75 + 8/5 + 3,125 = 0,44 + 8/5 + 3,125 = 0,44 + 1,6 + 3,125 = 0,44 + 4,725 = 5,165
4) 1,125 - 4/7 - 0,12 = 1,125 - (4/7) - 0,12 = 1,125 - 0,57 - 0,12 = 0,435 - 0,12 = 0,315
5) (1/3 + 0,4) × 3,5 + (1/6 + 0,75) × 6/5
a) \(0,75\times26+49\times\frac{3}{4}+\frac{3}{4}\times24+\) \(0,75\)
\(=\) \(0,75\times\left(26+1\right)+\frac{3}{4}\times\left(49+24\right)\)
\(=\) \(\frac{3}{4}\times27+\frac{3}{4}\times73\)
\(=\) \(\frac{3}{4}\times\left(27+73\right)\)
\(=\)\(\frac{3}{4}\times100=75\)
b) câu b,c làm tương tự
\(\left(\frac{7}{2}+2x\right).\frac{8}{3}=\frac{16}{3}\)
\(\frac{7}{2}+2x=\frac{16}{3}:\frac{8}{3}\)
\(\frac{7}{2}+2x=2\)
\(2x=2-\frac{7}{2}\)
\(2x=\frac{-3}{2}\)
\(x=\frac{-3}{2}:2\)
\(x=\frac{-3}{4}\)
\(\frac{1}{3}.x+0,5x=0,75\)
\(\frac{1}{3}x+\frac{1}{2}x=\frac{3}{4}\)
\(x.\left(\frac{1}{3}+\frac{1}{2}\right)=\frac{3}{4}\)
\(x.\frac{5}{6}=\frac{3}{4}\)
\(x=\frac{3}{4}:\frac{5}{6}\)
\(x=\frac{9}{10}\)
a) \(210:x=2,1:0,25=8,4\)
\(x=210:8,4=25\)
b) \(x.2+x.0,5=6,25\)
\(2,5x=6,25\)
\(x=6,25:2,5=2,5\)
c) \(x:0,25-x=15,6\)
\(3x=15,6\)
\(x=5,2\)
d) \(x:12,5=3,75.4=15\)
\(x=15.12,5=187,5\)
e) \(x.12,6-x.5,6=42\)
\(7x=42\)
\(x=6\)
g) \(x:0,1-x:4-x.0,75=2,25\)
\(10x-\dfrac{x}{4}-\dfrac{3x}{4}=2,25\)
\(9x=2,25\)
\(x=0,25\)
= 0,75 x 0,25 + 0,75 x 1,25 - 0,75 x 0,5
= 0,75 x ( 0,25 + 1,25 - 0,5 )
= 0,75 x 1
= 0,75
a. \(\frac{5}{12}:x=\left(\frac{5}{6}-\frac{1}{2}\right)\times\frac{5}{4}\)
\(=>\)\(\frac{5}{12}:x=\frac{1}{3}\times\frac{5}{4}=\frac{5}{12}\)
\(=>x=\frac{5}{12}:\frac{5}{12}=1\)
b.\(x:0,15=\left(2,8+0,38\right):0,75\)
\(=>x:0,15=3,18:0,75=4,24\)
\(=>x=4,24\times0,15=0,636\)