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35/27 x 18/49 = 35x18/27x49 = 630/1323 = 10/21
18/25 x 36/125 = 18x36/25x125 = 648/3125
mình ko bt đúng ko nữa nếu sai thì thông cảm nha
các bạn có cách nào mà làm mẫu số chung nhỏ nhất mà ko cần rút gọn được ko
\(\frac{8}{5}-\frac{18}{27}\)
\(=\frac{8}{5}-\frac{2}{3}\)
\(=\frac{24}{15}-\frac{10}{15}\)
\(=\frac{14}{15}\)
\(\frac{12}{20}-\frac{6}{18}\)
\(=\frac{3}{5}-\frac{1}{3}\)
\(=\frac{9}{15}-\frac{5}{15}\)
\(=\frac{4}{15}\)
\(\frac{8}{24}-\frac{5}{25}\)
\(=\frac{1}{3}-\frac{1}{5}\)
\(=\frac{5}{15}-\frac{3}{15}\)
\(=\frac{2}{15}\)
\(\frac{18}{21}-\frac{12}{27}\)
\(=\frac{6}{7}-\frac{4}{9}\)
\(=\frac{54}{63}-\frac{28}{63}\)
\(=\frac{26}{63}\)
1)8/5-2/3=14/15
2)3/5-1/3=4/15
3)1/3-1/5=2/15
4)6/7-4/9=26/63
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,\(\frac{7}{4}.\frac{11}{21}+\frac{11}{21}.\frac{5}{4}=\frac{11}{21}.\left(\frac{7}{4}+\frac{5}{4}\right)\)=\(\frac{11}{21}.3=\frac{11}{7}\)
Rút gọn:
\(\frac{18}{30}=\frac{18:6}{30:6}=\frac{3}{5}\)
\(\frac{36}{27}=\frac{36:9}{27:9}=\frac{4}{3}\)
\(\frac{64}{80}=\frac{64:16}{80:16}=\frac{4}{5}\)
\(\frac{45}{35}=\frac{45:5}{35:5}=\frac{9}{7}\)
\(\frac{12}{18}+\frac{1}{3}+\frac{1}{7}+\frac{2}{8}+\frac{27}{36}+\frac{42}{49}\)
\(=\frac{2}{3}+\frac{1}{3}+\frac{1}{7}+\frac{1}{4}+\frac{3}{4}+\frac{6}{7}\)
\(=\left(\frac{2}{3}+\frac{1}{3}\right)+\left(\frac{1}{7}+\frac{6}{7}\right)+\left(\frac{1}{4}+\frac{3}{4}\right)\)
\(=1+1+1\)
\(=3\)
các phân số bằng nhau là :
\(\frac{15}{25}=\frac{21}{35}=\frac{3}{5}=\frac{75}{125}\)
\(\frac{7}{4}=\frac{49}{28}=\frac{105}{60}\)
Rút gọn các phân số sau :
\(\frac{18}{30}=\frac{18\div6}{30\div6}=\frac{3}{5}\)
\(\frac{64}{80}=\frac{64\div16}{80\div16}=\frac{4}{5}\)
\(\frac{36}{27}=\frac{36\div9}{27\div9}=\frac{4}{3}\)
\(\frac{45}{35}=\frac{45\div5}{35\div5}=\frac{9}{7}\)
Ta có: \(\frac{54}{11}.\frac{121}{27}< n< \frac{100}{21}:\frac{25}{126}\)
\(\Rightarrow\frac{2.11}{1.1}< n< \frac{100}{21}.\frac{126}{25}\)
\(\Rightarrow22< n< 24\)
\(\Rightarrow n=23\)
Ta có:
\(\frac{54}{11}\cdot\frac{121}{27}=\frac{54\cdot121}{11\cdot27}=22\)
\(\frac{100}{21}:\frac{25}{126}=\frac{100}{21}\cdot\frac{126}{25}=\frac{100\cdot126}{21\cdot25}=24\)
\(\Rightarrow22< n< 24\)
\(\Rightarrow x=23\)
\(\frac{35}{27}.\frac{18}{49}=\frac{35.18}{27.49}=\frac{630}{1323}=\frac{10}{21}\)
\(\frac{18}{25}.\frac{36}{125}=\frac{18.36}{25.125}=\frac{648}{3125}\)
\(\frac{10}{21}\);\(\frac{648}{3125}\)