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\(\frac{3}{15}\)= \(\frac{3:3}{15:3}\) = \(\frac{1}{5}\)
\(\frac{33}{44}\)= \(\frac{33:11}{44:11}\)= \(\frac{3}{4}\)
\(\frac{2}{8}\)= \(\frac{2:2}{8:2}\)= \(\frac{1}{4}\)
\(\frac{1}{5}\)= \(\frac{1\times4}{5\times4}\)= \(\frac{4}{20}\)
\(\frac{3}{4}\)=\(\frac{3\times5}{4\times5}\)= \(\frac{15}{20}\)
\(\frac{1}{4}\)= \(\frac{1\times5}{4\times5}\)= \(\frac{5}{20}\)
\(\frac{9}{12}\)=\(\frac{9:3}{12:3}\) = \(\frac{3}{4}\)
\(\frac{24}{36}\)=\(\frac{24:12}{36:12}\)= \(\frac{2}{3}\)
\(\frac{3}{8}\)= \(\frac{3:1}{8:1}\)= \(\frac{3}{8}\)
\(\frac{3}{4}\)=\(\frac{3\times6}{4\times6}\)= \(\frac{18}{24}\)
\(\frac{2}{3}\)=\(\frac{2\times8}{3\times8}\)=\(\frac{16}{24}\)
\(\frac{3}{8}\)= \(\frac{3\times3}{8\times3}\)=\(\frac{9}{24}\)
3/15= 1/5; 33/44=3/4; 2/8= 1/4
1/5= 1x 4/ 5x4= 4/20; 3/4= 3x 5/ 4x 5= 15/20; 1/4= 1x 5/ 4x 5= 5/20
9/12= 3/4; 24/36= 2/3; 3/8 không rút gọn được
3/4= 3x 6/ 4x6= 18/24; 2/3= 2x 8/ 3x 8= 16/24; 3/8= 3x 3/ 8x 3= 9/24
Tổng của ba phân số đó là : \(\left(\frac{31}{24}+\frac{7}{8}+\frac{11}{12}\right)\div2=\frac{37}{24}\)
Phân số thứ nhất là : \(\frac{37}{24}-\frac{7}{8}=\frac{2}{3}\)
Phân số thứ hai là : \(\frac{37}{24}-\frac{11}{12}=\frac{5}{8}\)
Phân số thứ ba là : \(\frac{37}{24}-\frac{31}{24}=\frac{1}{4}\)
#Death.Hunter
a: 5/3=25/15
33/55=3/5=9/15
b: 5/7=15/21
6/21=6/21
c: 5/7=20/28
20/28=20/28
\(\frac{4}{3x6}\)+ \(\frac{4}{6x9}\)+ \(\frac{4}{9x12}\)+ \(\frac{4}{12x15}\)
= \(\frac{4}{18}\)+ \(\frac{4}{54}\)+ \(\frac{4}{108}\)+ \(\frac{4}{180}\)
= \(\frac{2}{9}\)+ \(\frac{2}{27}\)+ \(\frac{1}{27}\)+ \(\frac{1}{45}\)
= \(\frac{2}{27}\)+ \(\frac{1}{27}\)+ \(\frac{2}{9}\)+ \(\frac{1}{45}\)
= \(\frac{1}{9}\)+ \(\frac{2}{9}\)+ \(\frac{1}{45}\)
=\(\frac{3}{9}\)+ \(\frac{1}{45}\)
= \(\frac{4}{45}\)
Bài 1
\(\dfrac{1}{2}+\dfrac{7}{10}=\dfrac{5}{10}+\dfrac{7}{10}=\dfrac{12}{10}=\dfrac{6}{5}\)
\(\dfrac{8}{15}\times\dfrac{5}{12}=\dfrac{40}{180}=\dfrac{2}{9}\)
Baì 2
\(30\times\dfrac{5}{3}=50\)
\(\dfrac{6}{5}\times\dfrac{5}{3}=2\)
\(\dfrac{12}{40}\times\dfrac{5}{3}=\dfrac{1}{2}\)
\(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}\)
\(=1-\left(\frac{1}{2}-\frac{1}{2}\right)-\left(\frac{1}{3}-\frac{1}{3}\right)-......-\left(\frac{1}{6}-\frac{1}{6}\right)-\frac{1}{7}\)
\(=1-\frac{1}{7}\)
\(=\frac{6}{7}\)
1/2+1/6+1/12+1/20+1/30+1/42
=1/1x2+1/2x3+1/3x4+1/4x5+1/5x6+1/6x7
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7
=1-1/7
=6/7
\(\frac{8}{12};\frac{12}{15};\frac{15}{20}\)
MSC : 60
\(\frac{8}{12}=\frac{8\times5}{12\times5}=\frac{40}{60}\)
\(\frac{12}{15}=\frac{12\times4}{15\times4}=\frac{48}{60}\)
\(\frac{15}{20}=\frac{15\times3}{20\times3}=\frac{45}{60}\)
Vậy quy đồng mẫu số 3 phân số \(\frac{8}{12};\frac{12}{15};\frac{15}{20}\) ta được \(\frac{40}{60};\frac{48}{60};\frac{45}{60}\)
\(MSC:60\)
\(\frac{8}{12}=\frac{40}{60}\)
\(\frac{12}{15}=\frac{48}{60}\)
\(\frac{15}{20}=\frac{45}{60}\)
HT