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a) ( 42- 6) : 1/2 + 7/6
= 36 : 1/2 + 7/6
= 72 + 7/6
= 439/6
b) 18/5 - 2/7 + 1/3
= 383/105
1)
a)\(\dfrac{20}{30}+\dfrac{9}{30}=\dfrac{29}{30}\)
b)\(\dfrac{16}{24}-\dfrac{15}{24}=\dfrac{1}{24}\)
c)\(\dfrac{12}{63}=\dfrac{4}{21}\)
d) \(\dfrac{5}{6}x\dfrac{3}{4}=\dfrac{15}{24}=\dfrac{5}{8}\)
2)
a)\(x=\dfrac{5}{4}-\dfrac{2}{3}\)
\(x=\dfrac{7}{12}\)
b) \(x=4x\dfrac{3}{5}\)
\(x=\dfrac{12}{5}\)
bài 1
a)\(=\dfrac{16}{40}+\dfrac{15}{40}=\dfrac{31}{40}\)
b)\(=\dfrac{7}{6}-\dfrac{4}{6}=\dfrac{3}{6}=\dfrac{1}{2}\)
c)\(=\dfrac{30}{9}=\dfrac{10}{3}\)
d)\(=\dfrac{8}{5}\times\dfrac{7}{4}=\dfrac{56}{20}=\dfrac{14}{5}\)
\(\dfrac{7}{5}\times\dfrac{3}{4}:\dfrac{4}{5}=\dfrac{21}{20}:\dfrac{4}{5}=\dfrac{21}{20}\times\dfrac{5}{4}=\dfrac{105}{80}\)
\(x-\dfrac{3}{9}=\dfrac{8}{7}\)
\(x=\dfrac{8}{7}+\dfrac{3}{9}\)
\(x=\dfrac{72}{63}+\dfrac{21}{63}\)
\(x=\dfrac{93}{63}\)
bài 1 :
\(a,\dfrac{2}{7}+\dfrac{1}{3}=\dfrac{6}{21}+\dfrac{7}{21}=\dfrac{13}{21}\)
\(b,\dfrac{3}{5}-\dfrac{1}{3}=\dfrac{9}{15}-\dfrac{5}{15}=\dfrac{4}{15}\)
\(c,\dfrac{13}{4}:5=\dfrac{13}{4}:\dfrac{5}{1}=\dfrac{13}{4}x\dfrac{1}{5}=\dfrac{13}{20}\)
\(d,\dfrac{6}{23}x\dfrac{1}{18}=\dfrac{1}{69}\)
bài 2 :
\(a,x+\dfrac{1}{3}=\dfrac{5}{12}\)
\(x=\dfrac{5}{12}-\dfrac{1}{3}\)
\(x=\dfrac{1}{12}\)
\(b,x:\dfrac{7}{4}=\dfrac{2}{5}\)
\(x=\dfrac{2}{5}x\dfrac{7}{4}\)
\(x=\dfrac{7}{10}\)
bài 3 :
đổi : 2 dm 1cm = 21cm
chiều cao hình bình hành là;
21 x\(\dfrac{3}{7}=\)9(cm)
diện tích hình bình hành là;
21 x 9 =189 (cm2)
đáp số : 189 cm2
bài 4 :
\(\dfrac{2}{3}x\dfrac{2}{10}+\dfrac{2}{3}x\dfrac{5}{10}x\dfrac{3}{3}\)
\(\dfrac{2}{3}x\left(\dfrac{2}{10}+\dfrac{5}{10}\right)x\dfrac{2}{3}\)
=\(\dfrac{2}{3}x1x\dfrac{2}{3}\)
\(=\dfrac{2}{3}x\dfrac{2}{3}\)
=\(\dfrac{4}{9}\)
Bài 1)
a) \(\dfrac{6}{21}+\dfrac{7}{21}=\dfrac{13}{21}\)
b) \(\dfrac{9}{15}-\dfrac{5}{15}=\dfrac{4}{15}\)
c) \(\dfrac{13}{4}x\dfrac{1}{5}=\dfrac{13}{20}\)
d) \(\dfrac{6}{414}=\dfrac{1}{69}\)
Bài 2)
a) \(x=\dfrac{5}{12}-\dfrac{1}{3}\)
\(x=\dfrac{1}{12}\)
b) \(x=\dfrac{2}{5}x\dfrac{7}{4}\)
\(x=\dfrac{7}{10}\)
Bài 3)
2dm 1cm = 21 cm
Chiều cao tấm bìa la
\(21x\dfrac{3}{7}=9\left(cm\right)\)
Diện tích tấm bìa là
\(21x9=189\left(cm2\right)\)
\(\dfrac{9}{5}-\dfrac{3}{4}:\dfrac{5}{6}=\dfrac{9}{5}-\dfrac{9}{10}=\dfrac{9}{10}\)
\(x=\dfrac{7}{9}:\dfrac{5}{7}=\dfrac{49}{45}\)
\(=\dfrac{9}{5}-\dfrac{3}{4}x\dfrac{6}{5}=\dfrac{9}{5}-\dfrac{9}{10}=\dfrac{18}{10}-\dfrac{9}{10}=\dfrac{9}{10}\)
\(x=\dfrac{7}{9}:\dfrac{5}{7}\)
\(x=\dfrac{49}{45}\)
a \(\dfrac{6}{15}+\dfrac{11}{15}=\dfrac{17}{15}\)
b \(\dfrac{22}{77}-\dfrac{14}{77}=\dfrac{8}{77}\)
c \(\dfrac{11}{13}\times\dfrac{26}{31}=11\times\dfrac{2}{31}=\dfrac{22}{31}\)
d \(\dfrac{1}{2}\times3\times\dfrac{2}{5}=\dfrac{3}{5}\)
Bài 2:
\(=\dfrac{28}{25}\cdot\dfrac{15}{7}\cdot5=\dfrac{75}{25}\cdot4=12\)
Bài 1:
a: \(x+\dfrac{7}{8}=\dfrac{13}{2}:4=\dfrac{13}{8}\)
nên x=13/8-7/8=6/8=3/4
b: \(x:\dfrac{5}{3}=\dfrac{6}{5}-\dfrac{2}{3}=\dfrac{18-10}{15}=\dfrac{8}{15}\)
nên \(x=\dfrac{8}{15}\cdot\dfrac{5}{3}=\dfrac{8}{9}\)