Tính bằng cách thuận tiện
15/7:4/5-8/7:4/5
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\(\frac{1}{5}+\frac{5}{7}+\frac{1}{8}+\frac{13}{8}+\frac{4}{5}+\frac{4}{7}\)
\(=\left(\frac{1}{5}+\frac{4}{5}\right)+\left(\frac{5}{7}+\frac{4}{7}\right)+\left(\frac{1}{8}+\frac{13}{8}\right)\)
\(=1+\frac{9}{7}+\frac{7}{4}\)
\(=\frac{28}{28}+\frac{36}{28}+\frac{49}{28}\)
\(=\frac{113}{28}\)
Ai k mik mik k lại
\(\left(\dfrac{2}{7}+\dfrac{5}{7}\right)+\left(\dfrac{3}{5}+\dfrac{2}{5}\right)+\left(\dfrac{3}{8}+\dfrac{4}{8}+\dfrac{1}{8}\right)+\left(\dfrac{1}{9}+\dfrac{8}{9}\right)=1+1+1+1=4\)
=39/16:5/8-7/16:5/8+4/5:5/8
=(39/16-7/16+4/5):5/8
= 14/5:5/8
=112/25
= ( 39/16 + 7/16 ) : 5/8 : 4/5
= 46/16 * 8/5 * 5/4
= 368/80 * 5/4
= 23/4
Chúc bạn học tốt !!!
4/3:5/4:6/5:7/6:8/7:9/8
=4/3*4/5*5/6*6/7*7/8*8/9
=4/3*4*1/9
=16/27
a) \(\dfrac{5}{9}+\dfrac{13}{7}+\dfrac{15}{13}+\dfrac{8}{7}+\dfrac{4}{9}+\dfrac{11}{13}\)
\(=\left(\dfrac{5}{9}+\dfrac{4}{9}\right)+\left(\dfrac{13}{7}+\dfrac{8}{7}\right)+\left(\dfrac{15}{13}+\dfrac{11}{13}\right)\)
\(=1+3+2\)
\(=6\)
b) \(\dfrac{3}{5}+\dfrac{18}{9}+\dfrac{4}{10}\)
\(=0,6+2+0,4\)
\(=\left(0,6+0,4\right)+2\)
\(=1+2\)
\(=3\)
\(a\dfrac{5}{9}+\dfrac{4}{9}+\dfrac{13}{7}+\dfrac{8}{7}+\dfrac{15}{13}+\dfrac{11}{13}=\dfrac{9}{9}+\dfrac{21}{7}+\dfrac{26}{13}=1+3+2=6\)
8/15 + 7/4 + 7/15 + 5/4
= 8/15 + 7/15 + 7/4 +5/4
= ( 8/15 + 7/15) + ( 7/4 + 5/4)
= 15/15 + 12/4
= 1 + 3
=4
\(5\dfrac{3}{4}:3+2\dfrac{1}{4}\times\dfrac{1}{3}-\dfrac{1}{8}=\left(5\dfrac{3}{4}+2\dfrac{1}{4}\right)\times\dfrac{1}{3}-\dfrac{1}{8}\\ =8\times\dfrac{1}{3}-\dfrac{1}{8}=\dfrac{8}{3}-\dfrac{1}{8}=\dfrac{61}{24}\\ ----\\ \dfrac{3}{5}:\dfrac{5}{6}:\dfrac{6}{7}:\dfrac{7}{8}+\dfrac{2}{5}+\dfrac{23}{35}\\ =\dfrac{3}{5}\times\dfrac{6}{5}\times\dfrac{7}{6}\times\dfrac{8}{7}+\dfrac{2}{5}+\dfrac{23}{35}=\dfrac{18}{25}\times\dfrac{4}{3}+\dfrac{2}{5}+\dfrac{23}{35}=\dfrac{353}{175}\)