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Bài 1:
a) \(2\frac{1}{4}+1\frac{1}{2}-1\frac{4}{5}\)
=\(\frac{9}{4}\)+\(\frac{3}{2}\)-\(\frac{9}{5}\)
=\(\frac{45}{20}+\frac{30}{20}-\frac{36}{20}\)
=\(\frac{39}{20}\)
b) \(2\frac{2}{3}\times3\frac{1}{4}:2\frac{3}{4}\)
\(\frac{8}{3}\times\frac{13}{4}:\frac{11}{4}\)
=\(\frac{8}{3}\times\frac{13}{4}\times\frac{4}{11}\)
=\(\frac{104}{33}\)
Bài 2:
a) \(\frac{7}{9}+\frac{4}{5}+\frac{11}{9}+\frac{6}{5}\)
=\(\left(\frac{7}{9}+\frac{11}{9}\right)+\left(\frac{4}{5}+\frac{6}{5}\right)\)
=2+2
=4
b) \(\frac{21}{36}\times\frac{39}{14}\times\frac{54}{13}\)
=\(\frac{21\times39\times54}{36\times14\times13}\)
=\(\frac{675}{100}\)
A=(6 : 35−116 x 67) : (415 x 1011+5211)A=(6 : 35−116 x 67) : (415 x 1011+5211)
A=(6 : 35−76 x 67) : (215 x 1011+5711)A=(6 : 35−76 x 67) : (215 x 1011+5711)
A=(10−1) : (4211+5711)A=(10−1) : (4211+5711)
A=9 : 9A=9 : 9
A=1
bài 1.tính bằng cách hợp lí nhất :
a) 1/7 + 2/7 + 3/7 + ..... 3 5/7 + 3 6/7
b) 3/5x 3 5/9 + 6/5 x 11/9
1.
=3/5x(3/7+4/7)+2/5x(13/9-4/9)
=3/5x1+2/5x1
=3/5+2/5
=1
2.Xx(3/4+4/5)=7/10
Xx31/20=7/10
X =7/10:31/20
X =14/31
\(\frac{3}{5}\cdot\frac{3}{7}+\frac{3}{5}\cdot\frac{4}{7}+\frac{2}{5}\cdot\frac{13}{9}-\frac{2}{5}\cdot\frac{4}{9}\)
\(=\frac{3}{5}\cdot\left(\frac{3}{7}+\frac{4}{7}\right)+\frac{2}{5}\cdot\left(\frac{13}{9}-\frac{4}{9}\right)\)
\(=\frac{3}{5}\cdot1+\frac{2}{5}\cdot1\)\(=\frac{3}{5}+\frac{2}{5}=1\)
_________________________________________
\(\frac{3}{4}\cdot x+\frac{4}{5}\cdot x=\frac{7}{10}\)
\(\left(\frac{3}{4}+\frac{4}{5}\right)\cdot x=\frac{7}{10}\)
\(\frac{31}{20}\cdot x=\frac{7}{10}\)
\(x=\frac{7}{10}:\frac{31}{20}\)
\(x=\frac{14}{31}\)
a, 67,8 x 2012 + 33,2 × 2012-2012
= 67,8×2012+33,2×2012-2012×1
=2012×(67,8+33,2-1)
=2012×100
=201200
b, 5/11 + 7/9 + 2/9 + 6/11 + 7/15
=( 5/11 + 6/11) + ( 7/9 +2/9) +7/15
=1 + 1 + 7/15
=2 + 7/15
=37/15
a, 67,8 x 2012 + 33,2 × 2012-2012
= 67,8×2012+33,2×2012-2012×1
=2012×(67,8+33,2-1)
=2012×100
=201200
b, 5/11 + 7/9 + 2/9 + 6/11 + 7/15
=( 5/11 + 6/11) + ( 7/9 +2/9) +7/15
=1 + 1 + 7/15
=2 + 7/15
=37/15
Nguyễn Vũ Mai Chi
Bài 1:
\(a.8,32+14,76+5,24=8,32+\left(14,76+5,24\right)\)
\(=8,32+20=28,32\)
\(b,16,88+9,76+3,12=\left(16,88+3,12\right)+9,76\)
\(=20+9,76=29,76\)
\(c,\left(\dfrac{2}{5}+\dfrac{7}{9}\right)+\dfrac{3}{5}=\left(\dfrac{2}{5}+\dfrac{3}{5}\right)+\dfrac{7}{9}\)
\(=1+\dfrac{7}{9}=\dfrac{16}{9}\)
\(d,\dfrac{19}{11}+\left(\dfrac{8}{13}+\dfrac{3}{11}\right)\)
\(=\left(\dfrac{19}{11}+\dfrac{3}{11}\right)+\dfrac{8}{13}=\dfrac{22}{11}+\dfrac{8}{13}\)
\(=2+\dfrac{8}{13}=\dfrac{34}{13}\)
