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G
20 tháng 2 2020
\(\frac{5}{6}\times\frac{7}{12}+\frac{5}{12}\times\frac{5}{6}+\frac{1}{6}\)
= \(\frac{35}{72}+\frac{25}{36}+\frac{1}{6}\)
= \(\frac{97}{72}\)
\(\left(\frac{8}{15}\times\frac{3}{4}\times\frac{5}{4}\right):\frac{7}{8}\)
= \(\frac{1}{2}:\frac{7}{8}\)
=\(\frac{4}{7}\)
HOK TỐT ^^
3 tháng 3 2020
\(1,\frac{5}{7}+\frac{3}{14}=\frac{10}{14}+\frac{3}{14}=\frac{13}{14}\)
\(2,\frac{11}{12}-\frac{5}{6}=\frac{11}{12}-\frac{10}{12}=\frac{1}{12}\)
\(3,6.\frac{5}{8}=\frac{30}{8}=\frac{15}{4}\)
\(4,\frac{4}{5}:\frac{3}{7}=\frac{4.7}{5.3}=\frac{28}{15}\)
3 tháng 3 2020
5/7+3/14=13/14
11/12-5/6=1/12
6*5/8=30/8
4/5:3/7=28/15
VT
20 tháng 8 2017
\(a,=\frac{7-1}{1.3.7}+\frac{9-3}{3.7.9}+\frac{13-7}{7.9.13}+\frac{15-9}{9.13.15}\)\(+\frac{19-13}{13.15.19}\)
\(=\frac{1}{1.3}-\frac{1}{3.7}+\frac{1}{3.7}-\frac{1}{7.9}+\frac{1}{7.9}-\frac{1}{9.13}+\frac{1}{9.13}-\frac{1}{13.15}+\frac{1}{13.15}-\frac{1}{15.19}\)
\(=\frac{1}{1.3}-\frac{1}{15.19}=\frac{95}{285}-\frac{1}{285}=\frac{94}{285}\)
\(b,=\frac{1}{6}.\left(\frac{6}{1.3.7}+\frac{6}{3.7.9}+\frac{6}{7.9.13}+\frac{6}{9.13.15}+\frac{6}{13.15.19}\right)\)
làm giống như trên
\(c,=\frac{1}{8}.\left(\frac{1}{1.2.3}+\frac{1}{2.3.4}+\frac{1}{3.4.5}+...+\frac{1}{48.49.50}\right)\)
\(=\frac{1}{16}.\left(\frac{2}{1.2.3}+\frac{2}{2.3.4}+\frac{2}{3.4.5}+...+\frac{2}{48.49.50}\right)\)
\(=\frac{1}{16}.\left(\frac{3-1}{1.2.3}+\frac{4-2}{2.3.4}+\frac{5-3}{3.4.5}+...+\frac{50-48}{48.49.50}\right)\)
\(=\frac{1}{16}.\left(\frac{1}{1.2}-\frac{1}{2.3}+\frac{1}{2.3}-\frac{1}{3.4}+\frac{1}{3.4}-\frac{1}{4.5}+...+\frac{1}{48.49}-\frac{1}{49.50}\right)\)
\(=\frac{1}{16}.\left(\frac{1}{2}-\frac{1}{2450}\right)=\frac{1}{16}.\left(\frac{1225}{2450}-\frac{1}{2450}\right)=\frac{153}{4900}\)
\(d,=\frac{5}{7}.\left(\frac{7}{1.5.8}+\frac{7}{5.8.12}+\frac{7}{8.12.15}+...+\frac{7}{33.36.40}\right)\)
\(=\frac{5}{7}.\left(\frac{8-1}{1.5.8}+\frac{12-5}{5.8.12}+\frac{15-8}{8.12.15}+...+\frac{40-33}{33.36.40}\right)\)
\(=\frac{5}{7}.\left(\frac{1}{1.5}-\frac{1}{5.8}+\frac{1}{5.8}-\frac{1}{8.12}+\frac{1}{8.12}-\frac{1}{12.15}+...+\frac{1}{33.36}-\frac{1}{36.40}\right)\)
\(=\frac{5}{7}.\left(\frac{1}{5}-\frac{1}{1440}\right)=\frac{5}{7}.\left(\frac{288}{1440}-\frac{1}{1440}\right)=\frac{41}{288}\)
P/S: . là nhân nha
15 tháng 9 2021
\(a,\frac{11}{12}:\frac{7}{24}\cdot\frac{21}{24}=\frac{11\cdot24\cdot7\cdot3}{4\cdot3\cdot7\cdot24}=\frac{11}{4}\)
\(b,\frac{5}{12}:\frac{7}{4}-\frac{25}{18}:\frac{35}{6}=\frac{5\cdot4}{3\cdot4\cdot7}-\frac{5\cdot5\cdot6}{6\cdot3\cdot5\cdot7}=\frac{5}{21}\)
17 tháng 10 2015
5/3 - 3/4 + 7/12 = 20/12 - 9/12 + 7/12 = 18/12 = 3/2
5/6 : 2 x 18/7 = 5/6 x 1/2 x 18/7 = 90/84 = 15//14
NN
Nguyễn Ngọc Anh Minh
CTVHS
VIP
9 tháng 10 2021
\(=\frac{5}{6}x\left(\frac{7}{12}+\frac{5}{12}\right)+\frac{1}{6}=\frac{5}{6}x1+\frac{1}{6}=1\)
9 tháng 10 2021
a) \(\frac{5}{6}x\frac{7}{12}+\frac{5}{12}x\frac{5}{6}+\frac{1}{6}=\frac{5}{6}x\left(\frac{7}{12}+\frac{5}{12}\right)+\frac{1}{6}=\frac{5}{6}x1+\frac{1}{6}=\frac{5}{6}+\frac{1}{6}=1\)
b) \(\left(\frac{8}{15}x\frac{3}{4}x\frac{5}{4}\right):\frac{7}{8}=\frac{4x2x3x5}{5x3x4x4}x\frac{8}{7}=\frac{2}{4}x\frac{8}{7}=\frac{2x8}{4x7}=\frac{2x4x2}{4x7}=\frac{4}{7}\)
Chúc bạn học tốt.
😁😁😁
7 tháng 8 2015
a) \(\frac{13}{7}-\frac{1}{2}\times\frac{13}{7}+\frac{3}{2}\times\frac{13}{7}\)
\(=\frac{13}{7}\times\left(1-\frac{1}{2}+\frac{3}{2}\right)\)
\(=\frac{13}{7}\times2\)
\(=\frac{26}{7}\)
b) \(\frac{1}{15}\times\left(\frac{3}{7}+\frac{5}{19}\right)+\frac{3}{7}\times\left(\frac{5}{19}-\frac{1}{15}\right)\)
\(=\frac{1}{15}\times\frac{3}{7}+\frac{1}{15}\times\frac{5}{19}+\frac{3}{7}\times\frac{5}{19}-\frac{3}{7}\times\frac{1}{15}\)
\(=\frac{5}{19}\times\left(\frac{1}{15}+\frac{3}{7}\right)\)
\(=\frac{5}{19}\times\frac{52}{105}\)
\(=\frac{52}{399}\)
c) \(\frac{5}{6}+\frac{5}{12}+\frac{5}{20}+\frac{5}{30}+...+\frac{5}{9900}\)
\(=5\times\left(\frac{1}{2\times3}+\frac{1}{3\times4}+\frac{1}{4\times5}+\frac{1}{5\times6}+...+\frac{1}{99\times100}\right)\)
\(=5\times\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+...+\frac{1}{99}-\frac{1}{100}\right)\)
\(=5\times\left(\frac{1}{2}-\frac{1}{100}\right)\)
\(=5\times\frac{49}{100}\)
\(=\frac{49}{20}\)
Lần sau nên đăng ít thôi
5 6 + 7 12 = 10 12 + 7 12 = 17 12