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\(a.\) \(\frac{4}{15}.\frac{7}{9}+\frac{4}{15}.\frac{2}{9}\)
\(=\frac{4}{15}\left(\frac{7}{9}+\frac{2}{9}\right)\)
\(=\frac{4}{15}.\frac{9}{9}\)
\(=\frac{4}{15}.1\)
\(=\frac{4}{15}\)
\(b.\) \(\frac{13}{19}.\frac{23}{11}-\frac{13}{19}.\frac{8}{11}-\frac{13}{19}.\frac{4}{11}\)
\(=\frac{13}{19}\left(\frac{23}{11}-\frac{8}{11}-\frac{4}{11}\right)\)
\(=\frac{13}{19}.\frac{11}{11}\)
\(=\frac{13}{19}.1\)
\(=\frac{13}{19}\)
a)4/15 x(7/9+2/9)=4/15x1=4/15
b)13/19x(23/11-8/11-4/11)13/19x1=13/19
a) $\frac{1}{6} \times \frac{2}{3} = \frac{{1 \times 2}}{{6 \times 3}} = \frac{2}{{18}} = \frac{1}{9}$
b) $\frac{6}{5} \times \frac{3}{8} = \frac{{6 \times 3}}{{5 \times 8}} = \frac{{18}}{{40}} = \frac{9}{{20}}$
c) $\frac{4}{3} \times \frac{8}{9} = \frac{{4 \times 8}}{{3 \times 9}} = \frac{{32}}{{27}}$
d) $\frac{5}{{12}} \times \frac{{12}}{5} = \frac{{5 \times 12}}{{12 \times 5}} = \frac{{60}}{{60}} = 1$
a) \(\frac{16}{35}+\frac{8}{35}=\frac{24}{35}\)
b)\(\frac{160}{77}-\frac{28}{77}=\frac{132}{77}=\frac{12}{1}=12\)
c)\(\frac{72}{180}=\frac{18}{45}\)
d) \(\frac{90}{360}=\frac{1}{4}\)
\(\frac{3}{4}\)x \(\frac{4}{8}\)+ \(\frac{6}{8}\)
= \(\frac{3}{8}\)+ \(\frac{6}{8}\)
= \(\frac{9}{8}\)
câu 2:
A = 1/1*2 + 1/2*3 + 1/3*4 + ... + 1/98*99 + 1/99*100
A = 2-1/1*2 + 3-2/2*3 + 4-3/3*4 + ... + 99-98/98*99 + 100-99/99*100
A = 2/1*2 - 1/ 1*2 + 3/2*3 - 2/2*3 + 4/ 3*4 -3/3*4 +...+ 99/98*99 - 98/98*99 + 100/99*100 - 99/99*100
A = 1 - 1/ 100
A = 99 / 100
phần 2 mk ko =bít
bài 1, 3 mk ko bít
a) $\frac{1}{6} \times ...... = \frac{1}{6}$
$\frac{1}{6}:\frac{1}{6} = 1$
b) $......\, \times \frac{4}{7} = 0$
$0:\frac{4}{7} = 0$
c) $\frac{5}{8}:...... = \frac{5}{8}$
$\frac{5}{8}:\frac{5}{8} = 1$
a) $\frac{2}{7}:\frac{4}{9} = \frac{2}{7} \times \frac{9}{4}$
b) $\frac{{12}}{{25}}:\frac{6}{5} = \frac{{12}}{{25}} \times \frac{5}{6}$
c) $\frac{5}{8}:3 = \frac{5}{8}:\frac{3}{1} = \frac{5}{8} \times \frac{1}{3}$
a) \(4\frac{3}{8}+5\frac{2}{3}=4+\frac{3}{8}+5+\frac{2}{3}\)
\(=\left(4+5\right)+\left(\frac{3}{8}+\frac{2}{3}\right)\)
\(=9+\frac{25}{24}=9+1\frac{1}{24}=9+1+\frac{1}{24}\)
\(=10+\frac{1}{24}=10\frac{1}{24}\)
b ) \(\frac{5}{2}\cdot\frac{1}{3}+\frac{1}{4}=\frac{5}{6}+\frac{1}{4}=\frac{13}{12}=1\frac{1}{12}\)
a) 35/8+17/3= 105/24+135/24=241/24
b) 5/2*1/3+1/4= 5/6+1/4= 20/24+6/24=13/12
6:13/4 = 6x4/13 = 24/13
duyệt đi
8x3/4:13/4
=6:13/4=24/13