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5 tháng 10 2021
\(\dfrac{8}{9}:\dfrac{3}{7}=\dfrac{56}{27}\\ \dfrac{8}{9}+\dfrac{2}{5}=\dfrac{58}{45}\\ \dfrac{7}{8}-\dfrac{1}{3}=\dfrac{13}{24}\\ \dfrac{3}{10}\times\dfrac{1}{6}=\dfrac{1}{20}\\ 1\dfrac{2}{7}+6\dfrac{5}{6}=\dfrac{9}{7}+\dfrac{41}{6}=\dfrac{341}{42}\\ 5\dfrac{3}{4}-\dfrac{1}{5}=\dfrac{23}{4}-\dfrac{1}{5}=\dfrac{111}{20}\\ 6\dfrac{2}{9}:4\dfrac{7}{10}=\dfrac{56}{9}:\dfrac{47}{10}=\dfrac{560}{423}\\ \dfrac{5}{3}+\dfrac{3}{2}-\dfrac{7}{6}=2\)
MN
7
AK
1 tháng 6 2018
\(\frac{1}{3}+\frac{3}{7}+\frac{5}{3}+\frac{8}{14}\)
\(=\left(\frac{1}{3}+\frac{5}{3}\right)+\left(\frac{3}{7}+\frac{8}{14}\right)\)
\(=\frac{6}{3}+\left(\frac{6}{14}+\frac{8}{14}\right)\)
\(=2+\frac{14}{14}\)
\(=2+1\)
\(=3\)
\(\frac{5}{6}+\frac{4}{15}+\frac{6}{18}+\frac{3}{45}\)
\(=\left(\frac{5}{6}+\frac{6}{18}\right)+\left(\frac{4}{15}+\frac{3}{45}\right)\)
\(=\left(\frac{5}{6}+\frac{2}{6}\right)+\left(\frac{4}{15}+\frac{1}{15}\right)\)
\(=\frac{7}{6}+\frac{5}{15}\)
\(=\frac{7}{6}+\frac{1}{3}\)
\(=\frac{7}{6}+\frac{2}{6}\)
\(=\frac{9}{6}\)
\(=\frac{3}{2}\)
~ Ủng hộ nhé
AK
1 tháng 6 2018
\(9\times17+83\times9\)
\(=\left(83+17\right)\times9\)
\(=100\times9\)
\(=900\)
\(4\frac{1}{7}+7+8\frac{6}{7}\)
\(=\left(4\frac{1}{7}+8\frac{6}{7}\right)+7\)
\(=\left(8+4\right)+\left(\frac{1}{7}+\frac{6}{7}\right)+7\)
\(=12+\frac{7}{7}+7\)
\(=12+1+7\)
\(=20\)
~ Ủng hộ nhé
DN
1
VH
1 tháng 4 2023
Bài 2. > , < , = ?
5/7 < 4/3 2/5 < 6/10 1/4 = 3/12 27/36 >
2/9 7/6 > 7/9
7/2 = 2/7 15/23 < 1 27/9 > 2 14/15 < 1 51/17 < 4
10 tháng 8 2022
1.3.77−1+3.7.99−3+7.9.1313−7+9.13.1515−9+\frac{19-13}{13.15.19}+13.15.1919−13
=\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}=1.31−3.71+3.71−7.91+7.91−9.131+9.131−13.151+13.151−15.191
=\frac{1}{1.3}-\frac{1}{15.19}=\frac{95}{285}-\frac{1}{285}=\frac{94}{285}=1.31−15.191=28595−2851=28594
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)b,=61.(1.3.76+3.7.96+7.9.136+9.13.156+13.15.196)
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)c,=81.(1.2.31+2.3.41+3.4.51+...+48.49.501)
=\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)=161.(1.2.32+2.3.42+3.4.52+...+48.49.502)
=\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)=161.(1.2.33−1+2.3.44−2+3.4.55−3+...+48.49.5050−48)
=\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)=161.(1.21−2.31+2.31−3.41+3.41−4.51+...+48.491−49.501)
=\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}=161.(21−24501)=161.(24501225−24501)=4900153
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)d,=75.(1.5.87+5.8.127+8.12.157+...+33.36.407)
=\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)=75.(1.5.88−1+5.8.1212−5+8.12.1515−8+...+33.36.4040−33)
=\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)=75.(1.51−5.81+5.81−8.121+8.121−12.151+...+33.361−36.401)
=\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}=75.(51−14401)=75.(1440288−14401)=28841
P/S: . là nhân nha
OC
1
13 tháng 6 2016
\(\frac{1.2.3.4.5.6.7.8.9}{10.2.3.4.5.6.7.8.9}\)
Rút gọn bằng:
\(\frac{1.2.3.4.5.6.7.8.9}{10.2.3.4.5.6.7.8.9}\)\(=\frac{1}{10}\)
OC
2
13 tháng 6 2016
1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 = 362880
10 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 = 3628800
7/9 + 9/10 = 151/90
5/6 + 7/8 = 41/24
3/5 + 1/2 + 3/10 = 7/5
7/9 + 9/10 =70/90 + 81/90 =151/90=1/61/90
5/6 + 7/8 =40/48 +42/48 =82/48=1/17/24
3/5 + 1/2 + 3/10 =6/10+5/10+3/10=14/10=1/2/5