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a)\(\frac{8}{13}+\frac{4}{9}+\frac{1}{3}+\frac{5}{13}+3\)
\(=\left(\frac{8}{13}+\frac{5}{13}\right)+\left(\frac{4}{9}+\frac{1}{3}\right)+3\)
\(=1+\left(\frac{4}{9}+\frac{3}{9}\right)+3\)
\(=1+\frac{7}{9}+3\)
\(=1+3+\frac{7}{9}\)
\(=4\frac{7}{9}\)
\(=\frac{43}{9}\)
b)\(\frac{8}{5}\cdot\frac{4}{7}+\frac{4}{7}\cdot\frac{2}{5}-1\)
\(=\frac{4}{7}\cdot\left(\frac{8}{5}+\frac{2}{5}\right)-1\)
\(=\frac{4}{7}\cdot2-1\)
\(=\frac{8}{7}-1\)
\(=\frac{1}{7}\)
a) \(\frac{8}{13}+\frac{4}{9}+\frac{1}{3}+\frac{5}{13}+3\)
\(=\left(\frac{8}{13}+\frac{5}{13}\right)+\left(\frac{4}{9}+\frac{3}{9}\right)+3\)
\(=1+\frac{7}{9}+3=4\frac{7}{9}\)
b)\(\frac{8}{5}.\frac{4}{7}+\frac{4}{7}.\frac{2}{5}-1\)
\(=\frac{4}{7}.\left(\frac{8}{5}+\frac{2}{5}\right)-1\)
\(=\frac{4}{7}.2-1\)
\(=\frac{8}{7}-\frac{7}{7}=\frac{1}{7}\)
a) \(\frac{3}{5}\times\frac{8}{27}\times\frac{5}{3}\)
\(=\left(\frac{3}{5}\times\frac{5}{3}\right)\times\frac{8}{27}\)
\(=1\times\frac{8}{27}\)
\(=\frac{8}{27}\)
b) \(\frac{7}{19}\times\frac{1}{3}+\frac{7}{19}\times\frac{2}{3}\)
\(=\frac{7}{19}\times\left(\frac{1}{3}+\frac{2}{3}\right)\)
\(=\frac{7}{19}\times1\)
\(=\frac{7}{19}\)
\(=\left(\frac{3}{5}+\frac{2}{5}\right)+\left(\frac{6}{11}+\frac{16}{11}\right)+\left(\frac{7}{13}+\frac{19}{13}\right)\)
\(=1+2+2\)
\(=5\)
\(\frac{7}{3}y+\frac{3}{5}\times2,5=3\)
\(\Leftrightarrow\frac{7}{3}y+\frac{3}{2}=3\)
\(\Leftrightarrow\frac{7}{3}y=3-\frac{3}{2}\)
\(\Leftrightarrow\frac{7}{3}y=\frac{3}{2}\)
\(\Leftrightarrow y=\frac{3}{2}\div\frac{7}{3}\)
\(\Leftrightarrow y=\frac{9}{14}\)
Vậy \(y=\frac{9}{14}\)
a) 2/9 +1/5 +7/9+4/5
=( 2/9+7/9)+(1/5+4/5)
=1+1=2
b) 1/12+3/16+5/12+5/16
=(1/12 +5/12)+(3/16+5/16)
=1/2 +1/2=1
a)\(\frac{21}{11}x\frac{22}{17}x\frac{68}{63}\)
=\(\frac{21x22x68}{11x17x63}\)
=\(\frac{21x11x2x17x4}{11x17x21x3}\)
=\(\frac{2x4}{3}\)
=\(\frac{8}{3}\)
b)\(\frac{5}{14}x\frac{7}{13}x\frac{26}{25}\)
=\(\frac{5x7x26}{14x13x25}\)
dễ mà
=5/9x7/4+13/9x7/4
=7/4x(5/9+13/9)
=7/4x18/9
=7/4x2
=7/2
nhớ chọn cho mih nha bn
\(=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{6.7}+\frac{1}{7.8}\)
\(=\frac{1}{1}-\frac{1}{8}\)
\(=\frac{7}{8}\)'
a)3/7
b)17.42
c)45
d)2
e)48
f)1237.5
g)7/13
rb
a, \(\frac{3}{7} \times \frac{2}{5} + \frac{3}{7} \times \frac{3}{5}\)
Đặt thừa số chung \(\frac{3}{7}\) :
\(= \frac{3}{7} \times \left(\frac{2}{5} + \frac{3}{5}\right)\)
\(= \frac{3}{7} \times \frac{5}{5}\)
\(= \frac{3}{7} \times 1 = \frac{3}{7}\)
b, \(3.75 + 7.42 + 6.25\)
Gộp các số có tổng là số tròn:
\(= (3.75 + 6.25) + 7.42\)
\(= 10 + 7.42 = 17.42\)
c, \(4.5 \times 9.2 + 4.5 \times 0.8\)
Đặt thừa số chung \(4.5\) :
\(= 4.5 \times (9.2 + 0.8)\)
\(= 4.5 \times 10 = 45\)
d, \(\frac{2}{3} + \frac{4}{7} + \frac{1}{3} + \frac{3}{7}\)
Nhóm các phân số có cùng mẫu số:
\(= \left(\frac{2}{3} + \frac{1}{3}\right) + \left(\frac{4}{7} + \frac{3}{7}\right)\)
\(= \frac{3}{3} + \frac{7}{7}\)
\(= 1 + 1 = 2\)
e, \(2.5 \times 4.8 \times 0.4\)
Nhóm các số có tích là số tròn:
\(= (2.5 \times 0.4) \times 4.8\)
\(= 1 \times 4.8 = 4.8\)
f, \(12.5 \times 99\)
Tách \(99 = 100 - 1\)
\(= 12.5 \times (100 - 1)\)
\(= 12.5 \times 100 - 12.5 \times 1\)
\(= 1250 - 12.5 = 1237.5\)
g, \(\frac{7}{13} \times \frac{9}{5} - \frac{7}{13} \times \frac{4}{5}\)
Đặt thừa số chung \(\frac{7}{13}\)
\(= \frac{7}{13} \times \left(\frac{9}{5} - \frac{4}{5}\right)\)
\(= \frac{7}{13} \times \frac{5}{5}\)
\(= \frac{7}{13} \times 1 = \frac{7}{13}\)
a: \(\frac37\times\frac25+\frac37\times\frac35\)
\(=\frac37\times\left(\frac25+\frac35\right)\)
\(=\frac37\times\frac55=\frac37\)
b: 3,75+7,42+6,25
=3,75+6.25+7,42
=10+7,42
=17,42
c: \(4,5\times9,2+4,5\times0,8\)
\(=4,5\times\left(9,2+0,8\right)\)
=4,5x10
=45
d: \(\frac23+\frac47+\frac13+\frac37\)
\(=\left(\frac23+\frac13\right)+\left(\frac47+\frac37\right)\)
=1+1
=2
e: 2,5x4,8x0,4
=4,8x(2,5x0,4)
=4,8x1
=4,8
f: \(12,5\times99\)
\(=12,5\times\left(100-1\right)\)
=12,5x100-12,5x1
=1250-12,5
=1237,5
g: \(\frac{7}{13}\times\frac95-\frac{7}{13}\times\frac45\)
\(=\frac{7}{13}\times\left(\frac95-\frac45\right)\)
\(=\frac{7}{13}\times\frac55=\frac{7}{13}\)