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\(\frac{4+7+17+19+14}{6+13+9+13+9+6}=\frac{61}{6x2+13x2+9x2}=\frac{61}{12+26+18}=\frac{61}{56}\)
Chúc em học tốt!
Bài này chủ yếu tính nhanh ở phần tử số, mẫu số không cần tính nhanh
a) $\frac{1}{6}:\frac{3}{7} = \frac{1}{6} \times \frac{7}{3} = \frac{7}{{18}}$
b) $\frac{5}{{12}}:\frac{1}{4} = \frac{5}{{12}} \times \frac{4}{1} = \frac{{5 \times 4}}{{12 \times 1}} = \frac{{5 \times 4}}{{4 \times 3 \times 1}} = \frac{5}{3}$
c) $\frac{4}{{15}}:\frac{8}{3} = \frac{4}{{15}} \times \frac{3}{8} = \frac{{4 \times 3}}{{15 \times 8}} = \frac{{4 \times 3}}{{5 \times 3 \times 4 \times 2}} = \frac{1}{{10}}$
d) $\frac{{18}}{5}:\frac{9}{{10}} = \frac{{18}}{5} \times \frac{{10}}{9} = \frac{{18 \times 10}}{{5 \times 9}} = \frac{{9 \times 2 \times 5 \times 2}}{{5 \times 9}} = 4$
a, \(\frac{6}{7}.\frac{16}{15}.\frac{7}{6}.\frac{21}{32}=\frac{6}{7}.\frac{7}{6}.\frac{16}{15}.\frac{21}{32}\)=\(1.\frac{16}{15}.\frac{21}{32}=\frac{7}{5.2}=\frac{7}{10}\)
Phần b T2
c,\(\frac{7}{4}.\frac{11}{21}+\frac{11}{21}.\frac{5}{4}=\frac{11}{21}.\left(\frac{7}{4}+\frac{5}{4}\right)\)=\(\frac{11}{21}.3=\frac{11}{7}\)
=( 1/12+9/12+2/12+1/12) + ( 2/7+5/7) + (10/20+9/20)
= 13/12 +1+19/20
đến đây bạn tự tính nha
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) $2 \times \frac{3}{{14}} = \frac{2}{1} \times \frac{3}{{14}} = \frac{{2 \times 3}}{{1 \times 14}} = \frac{6}{{14}} = \frac{3}{7}$
b) $3 \times \frac{4}{9} = \frac{3}{1} \times \frac{4}{9} = \frac{{3 \times 4}}{{1 \times 9}} = \frac{{12}}{9} = \frac{4}{3}$
c) $\frac{7}{{18}} \times 6 = \frac{7}{{18}} \times \frac{6}{1} = \frac{{7 \times 6}}{{18 \times 1}} = \frac{{42}}{{18}} = \frac{7}{3}$
d) $\frac{{19}}{{12}} \times 0 = \frac{{19}}{{12}} \times \frac{0}{1} = \frac{{19 \times 0}}{{12 \times 1}} = 0$
a/ \(\left[\frac{4}{6}+\frac{14}{6}\right]+\left[\frac{7}{13}+\frac{19}{13}\right]+\left[\frac{17}{9}+\frac{1}{9}\right]=\frac{18}{6}+\frac{26}{13}+\frac{18}{9}=3+2+2=7\)
4/6 + 7/13 + 17/9 + 19/13 + 1/9 + 14/6
= (4/6 + 14/6) + (7/13 + 19/13) + (17/9 + 1/9)
= 18/6 + 26/13 + 18/9
= 3 + 2 + 2
=7
1/9 + 7/12 + 2/9 + 1/12 + 4/12 + 6/9
= (1/9 + 2/9 + 6/9) + (7/12 + 1/12 + 4/12)
= 9/9 + 12/12
= 1 + 1
=2