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\(\dfrac{15}{24}-\dfrac{3}{8}-\dfrac{1}{6}=\dfrac{5}{8}-\dfrac{3}{8}-\dfrac{1}{6}=\dfrac{1}{4}-\dfrac{1}{6}=\dfrac{1}{12}\)

\(\dfrac{7}{13}\cdot\dfrac{5}{24}\cdot\dfrac{39}{75}=\dfrac{39}{13}\cdot\dfrac{5}{75}\cdot\dfrac{7}{24}=3\cdot\dfrac{1}{15}\cdot\dfrac{7}{24}=\dfrac{35}{24}\)

25 tháng 7 2021

`15/24-3/8-1/6`

`=15/24-9/24-4/24`

`=2/24`

`=1/12

d, `7/13 . 5/24 . 39/75`

`=(7.5.13.3)/(13.24.5.5.3)`

`=7/(24.5)`

`=7/120`

18 tháng 9 2023

\(2\dfrac{3}{13}x\dfrac{27}{58}x2\dfrac{15}{24}x\dfrac{8}{21}:\dfrac{3}{7}\)

\(\dfrac{29}{13}x\dfrac{27}{58}x\dfrac{63}{24}x\dfrac{8}{21}x\dfrac{7}{3}\)

\(\dfrac{9x7}{13x2}=\dfrac{63}{26}\)

18 tháng 9 2023

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a)<=>2/7:(13/24+5/24)   b)<=>15/24-9/24-4/24       c)=7.5.39/13.14.15

<=>2/7:3/4                        <=>2/24=1/12                      =3/2.3

<=>2/7x4/3                                                                    =1/2

<=>8/21                                     

4 tháng 8 2019

a. \(\frac{2}{7}:\frac{13}{24}+\frac{2}{7}:\frac{5}{24}\)

\(\frac{2}{7}:\left(\frac{13}{24}+\frac{5}{24}\right)\)

\(\frac{2}{7}:\frac{3}{4}\)

\(\frac{8}{21}\)

b. \(\frac{15}{24}-\frac{3}{8}-\frac{1}{6}\)

\(\frac{15}{24}-\frac{9}{24}-\frac{4}{24}\)

\(\frac{2}{24}=\frac{1}{12}\)

c. \(\frac{7}{13}.\frac{5}{14}.\frac{39}{15}\)

\(\frac{7.5.3.13}{13.2.7.3.5}\)

\(\frac{1}{2}\)

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

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18 tháng 3 2019

a)=2 giờ 40 phút + 1 giờ 15 phút 

=3 giờ 55 phút

b)=10 giờ 24 phút - 4 giờ

=6 giờ 24 phút

c)=3 giờ 34 phút nhân 4

=14 giờ 16 phút

d)=????????????????????

a) 2 giờ 40 phút + 25 phút x 3 = 2 giờ 40 phút + 75 phút = 2 giờ 40 phút + 1 giờ 15 phút = 3 giờ 55 phút

b) 5 giờ 12 phút x 2 - 4 giờ = 10 giờ 24 phút - 4 giờ = 6 giờ 24 phút

c) (2 giờ 45 phút + 49 phút) x 4 = 3 giờ 34 phút x 4 = 12 giờ 136 phút = 14 giờ 16 phút

d) (8 giờ 15 phút) : 5 + 1 giờ 24 phút = 5 giờ 195 phút + 1 giờ 24 phút = 6 giờ 219 phút = 9 giờ 39 phút

~Học tốt~

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

3 tháng 7

c; 17\(\dfrac{2}{31}\) - (\(\dfrac{15}{17}\) + 6\(\dfrac{2}{31}\))

= 17 + \(\dfrac{2}{31}\) - \(\dfrac{15}{17}\) - 6 - \(\dfrac{2}{31}\)

= (17 - 6)  - \(\dfrac{15}{17}\) + (\(\dfrac{2}{31}\) - \(\dfrac{2}{31}\))

= 11  - \(\dfrac{15}{17}\)+ 0

=    \(\dfrac{172}{17}\)

3 tháng 7

b; 130\(\dfrac{25}{28}\) + 120\(\dfrac{17}{35}\)

= 130 + \(\dfrac{25}{28}\) + 120 + \(\dfrac{17}{35}\)

= (130 + 120) + (\(\dfrac{25}{28}\) + \(\dfrac{17}{35}\))

= 250 + (\(\dfrac{125}{140}\) + \(\dfrac{68}{140}\))

= 250 +  \(\dfrac{193}{140}\)

= 250\(\dfrac{193}{140}\)

5 tháng 4 2023

6/8>5/7

9/15=3/5

24/36<75/100

5 tháng 4 2023

6/8>5/7

9/15=3/5

24/36<75/100

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