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ND
Nguyễn Đức Trí
VIP
3 tháng 8 2023
a) \(...=\dfrac{19}{8}:\dfrac{15}{4}x\dfrac{8}{3}=\dfrac{19}{8}x\dfrac{4}{15}x\dfrac{8}{3}=\dfrac{76}{45}\)
b) \(...=\dfrac{3}{2}:\dfrac{7}{3}:\dfrac{17}{6}=\dfrac{3}{2}x\dfrac{3}{7}x\dfrac{6}{17}=\dfrac{27}{119}\)
c) \(...=\dfrac{14}{3}-\dfrac{7}{4}:\dfrac{12}{5}=\dfrac{14}{3}-\dfrac{7}{4}x\dfrac{5}{12}=\dfrac{14}{3}-\dfrac{35}{48}=\dfrac{14x16}{48}-\dfrac{35}{48}=\dfrac{224}{48}-\dfrac{35}{48}=\dfrac{189}{48}=\dfrac{63}{16}\)
GN
GV Nguyễn Trần Thành Đạt
Giáo viên
3 tháng 8 2023
\(a,2\dfrac{3}{8}:3\dfrac{3}{4}\times2\dfrac{2}{3}\\ =\dfrac{2\times8+3}{8}:\dfrac{3\times4+3}{4}\times\dfrac{2\times3+2}{3}\\ =\dfrac{19}{8}:\dfrac{15}{4}\times\dfrac{8}{3}\\ =\dfrac{19\times4\times8}{8\times15\times3}=\dfrac{76}{45}\)
\(b,1\dfrac{1}{2}:\dfrac{7}{3}:2\dfrac{5}{6}\\ =\dfrac{3}{2}:\dfrac{7}{3}:\dfrac{2\times6+5}{6}\\ =\dfrac{3}{2}\times\dfrac{3}{7}\times\dfrac{6}{17}\\ =\dfrac{54}{238}=\dfrac{27}{119}\)
\(c,4\dfrac{2}{3}-1\dfrac{3}{4}:2\dfrac{2}{5}\\ =\dfrac{4\times3+2}{3}-\dfrac{1\times4+3}{4}:\dfrac{2\times5+2}{5}\\ =\dfrac{14}{3}-\dfrac{7}{4}:\dfrac{12}{5}\\ =\dfrac{14}{3}-\dfrac{7}{4}.\dfrac{5}{12}\\ =\dfrac{14}{3}-\dfrac{35}{48}\\ =\dfrac{14\times16-35}{48}=\dfrac{189}{48}=\dfrac{63}{16}\)
ND
Nguyễn Đức Trí
VIP
31 tháng 7 2023
\(4\dfrac{2}{3}+3\dfrac{2}{7}=\dfrac{14}{3}+\dfrac{23}{7}=\dfrac{14x7+23x3}{21}=\dfrac{167}{21}\)
\(8\dfrac{5}{9}:5\dfrac{1}{2}=\dfrac{77}{9}:\dfrac{11}{2}=\dfrac{77}{9}x\dfrac{2}{11}=\dfrac{14}{9}\)
\(6\dfrac{5}{7}:2\dfrac{1}{6}=\dfrac{47}{7}:\dfrac{13}{6}=\dfrac{47}{7}x\dfrac{6}{13}=\dfrac{282}{91}\)
\(1\dfrac{3}{4}x2\dfrac{5}{6}=\dfrac{7}{4}x\dfrac{17}{6}=\dfrac{119}{24}\)
\(5\dfrac{3}{4}-2=\dfrac{23}{4}-2=\dfrac{23}{4}-\dfrac{8}{4}=\dfrac{15}{4}\)
12 tháng 8 2023
a)\(a+a+a+\dfrac{1}{2}x2\dfrac{2}{5}+a+\dfrac{14}{5}+a=134\)
\(5xa+\dfrac{1}{2}x\dfrac{12}{5}+\dfrac{14}{5}=134\)
\(5xa+\dfrac{12}{10}+\dfrac{14}{5}=134\)
\(5xa+\dfrac{6}{5}+\dfrac{14}{5}=134\)
\(5xa+4=134\)
\(5xa=134-4=130\)
\(a=130:5=26\)
b)\(5\dfrac{4}{10}-yx\dfrac{3}{4}=\dfrac{2}{3}\)
\(\dfrac{54}{10}-yx\dfrac{3}{4}=\dfrac{2}{3}\)
\(yx\dfrac{3}{4}=\dfrac{54}{10}-\dfrac{2}{3}\)
\(yx\dfrac{3}{4}=\dfrac{71}{15}\)
\(y=\dfrac{71}{15}:\dfrac{3}{4}\)
\(y=\dfrac{284}{45}\)
DH
1
TN
19 tháng 6 2020
Bài 1: Tính
a) =1\(\frac{49}{60}\)
b) =2\(\frac{13}{30}\)
Bài 2: Tìm x
a) =4\(\frac{1}{21}\)
Riêng câu b) thì mk nghĩ là bạn viết lộn vì mk thấy cái chỗ xx3/4 là mk ko hiểu rồi
9 tháng 7 2018
\(a)\) \(S=1+\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+...+\frac{1}{2187}\)
\(S=1+\frac{1}{3}+\frac{1}{3^2}+\frac{1}{3^3}+...+\frac{1}{3^7}\)
\(3S=3+1+\frac{1}{3}+\frac{1}{3^2}+...+\frac{1}{3^6}\)
\(3S-S=\left(3+1+\frac{1}{3}+\frac{1}{3^2}+...+\frac{1}{3^6}\right)-\left(1+\frac{1}{3}+\frac{1}{3^2}+\frac{1}{3^3}+...+\frac{1}{3^7}\right)\)
\(2S=3+\frac{1}{3^7}\)
\(2S=\frac{3^8+1}{3^7}\)
\(S=\frac{3^8+1}{3^7}.\frac{1}{2}\)
\(S=\frac{3^8+1}{2.3^7}\)
Vậy \(S=\frac{3^8+1}{2.3^7}\)
Chúc bạn học tốt ~
E
5 tháng 4 2020
( \(\frac{4}{5}\)\(+\frac{3}{5}\)) \(\times\frac{2}{5}\)\(\div2\)
\(=\frac{7}{5}\)\(\times\frac{2}{5}\)\(\div2\)
= \(\frac{14}{25}\)\(\div2\)
= \(\frac{7}{25}\)
SM
1
12 tháng 6 2019
a) 1/5 x 19 x 2/3 x 10 x 1/2 x 3 x 1/38
= ( 1/5 x 10 ) x ( 19 x 1/38 ) x ( 2/3 x 1/2 ) x 3
= ( 2 x 1/2 ) x ( 1/3 x 3 )
= 1 x 1
= 1
b) 5/8 x 4 x 8/5 x 7 x 0,25 x 1/8
= ( 5/8 x 8/5 ) x (4 x 0,25 ) x ( 7 x 1/8 )
= 1 x 1 x 7/8
= 7/8
17 tháng 9 2018
\(2\frac{1}{2}\cdot2\frac{3}{4}=\frac{5}{2}\cdot\frac{11}{4}=\frac{55}{8}\)
17 tháng 9 2018
2 1/2 x 2 3/4 = 2 x 2 + 1 / 2 x 2 x 4 + 3 / 4 = 5/2 x 11/4 = 55/8
\(\left(\frac{4}{5}+\frac{1}{2}\right)\cdot\frac{2}{3}:2\)
\(=\left(\frac{8}{10}+\frac{5}{10}\right)\cdot\frac{2}{3}:\frac{2}{1}\)
\(=\frac{13}{10}\cdot\frac{2}{3}\cdot\frac{1}{2}\)
\(=\frac{26}{30}\cdot\frac{1}{2}\)
\(=\frac{26}{60}=\frac{13}{30}\)