\(A=\dfrac{1}{6}+\dfrac{1}{24}+\dfrac{1}{60}+...+\dfrac{1}{970200}\)
\(A=\dfrac{1}{1.2.3}+\dfrac{1}{2.3.4}+\dfrac{1}{3.4.5}+...+\dfrac{1}{98.99.100}\)
Ta có:
\(\dfrac{1}{1.2.3}=\dfrac{1}{2}\left(\dfrac{1}{1.2}-\dfrac{1}{2.3}\right)\);
\(\dfrac{1}{2.3.4}=\dfrac{1}{2}\left(\dfrac{1}{2.3}-\dfrac{1}{3.4}\right)\);
...;
\(\dfrac{1}{98.99.100}=\dfrac{1}{2}\left(\dfrac{1}{98.99}-\dfrac{1}{99.100}\right)\)
\(A=\dfrac{1}{2}\left(\dfrac{1}{1.2}-\dfrac{1}{2.3}+\dfrac{1}{2.3}-\dfrac{1}{3.4}+...+\dfrac{1}{98.99}-\dfrac{1}{99.100}\right)\)
\(A=\dfrac{1}{2}\left(\dfrac{1}{1.2}-\dfrac{1}{99.100}\right)\)
\(A=\dfrac{1}{2}\left(\dfrac{99.100-2}{200.99}\right)\)
\(A=\dfrac{1}{2}\left(\dfrac{98998}{200.99}\right)=\dfrac{49499}{19800}\)
 

\(\dfrac{11}{8}\times\dfrac{3}{2}\times\left(2-\dfrac{5}{6}\right)=\dfrac{33}{16}\times\dfrac{12-5}{6}\)

\(=\dfrac{33}{6}\times\dfrac{7}{16}=\dfrac{11}{2}\times\dfrac{7}{16}=\dfrac{77}{32}\)

\(5-\dfrac{16}{21}\times\dfrac{35}{48}\times6\)

\(=5-\dfrac{35}{21}\times\dfrac{16\times6}{48}\)

\(=5-\dfrac{5}{3}\times2=5-\dfrac{10}{3}=\dfrac{5}{3}\)

\(\dfrac{6}{7}\times\dfrac{2}{3}+\dfrac{2}{3}\times\dfrac{4}{7}+\dfrac{2}{7}\times\dfrac{4}{3}\)

\(=\dfrac{2}{3}\left(\dfrac{6}{7}+\dfrac{4}{7}+\dfrac{4}{7}\right)=\dfrac{2}{3}\times2=\dfrac{4}{3}\)

Sửa đề: \(\dfrac{18}{11}\times\dfrac{4}{5}-\dfrac{4}{5}\times\dfrac{7}{11}+\dfrac{3}{4}\times\dfrac{7}{15}\)

\(=\dfrac{4}{5}\left(\dfrac{18}{11}-\dfrac{7}{11}\right)+\dfrac{3}{4}\times\dfrac{7}{15}=\dfrac{4}{5}+\dfrac{21}{60}\)

\(=\dfrac{48}{60}+\dfrac{21}{60}=\dfrac{69}{60}=\dfrac{23}{20}\)

11/8 x 3/2 x ( 2 - 5/6)

= 11/8 x 3/2 x 7/6

= 11/8 x (3/2 x 7/6)

= 11/8 x 7/4

= 77/32

5 - 16/21 x 35/48 x 6

= (5 - 16/21) x (35/48 x 6)

= 89/21 x 35/8

= 89/3 x 5/8

= 445/24

6/7 x 2/3 + 2/3 x 4/7 + 2/7 x 4/3

= 6/7 x 2/3 + 2/3 x 4/7 + 2/7 x 2/3 x 2

= 6/7 x 2/3 + 2/3 x 4/7 + 4/7 x 2/3

= 2/3 x (6/7 + 4/7 + 4/7)

= 2/3 x 14/7

= 4/3

18/11 x 4/5 - 4/5 x 7/1 + 3/4 x 8/15

= 4/5 x (18/11 - 7) +  3/4 x 8/15

= ra âm nhé

3548x3298+3548x1502

=3548(3298+1502)

=3548x4800

=17030400

Ggfggfnihguhhj

\(\dfrac{1995}{1997}\times\dfrac{1990}{1993}\times\dfrac{997}{995}\times\dfrac{1993}{1995}\times\dfrac{1997}{1990}\)

\(=\dfrac{1995}{1995}\times\dfrac{1997}{1997}\times\dfrac{1990}{1990}\times\dfrac{1993}{1993}\times\dfrac{997}{995}\)

\(=\dfrac{997}{995}\)

Các câu trả lời nhé bạn giúp mình với huhu

Hồng ăn số phần bánh pizza là :

1 - 1/4 = 3/4 (số bánh)

Huệ ăn số phần bánh pizza là:

3/4 - 1/8 = 5/8 (số bánh)

An ăn số phần bánh pizza là :

3 x 5/8 = 15/8 (số bánh)

Cả ba bạn ăn được số phần bánh pizza là :

3/4 + 5/8 + 15/8 = 13/4 (số bánh)

Đáp số : 13/4 số bánh pizza

Số cái bánh pi-da bò 8 hiệp sĩ được chia là:

8x0,5=4(cái)

Số cái bánh pida gà 8 hiệp sĩ được chia là:

\(8\times\dfrac{1}{8}=1\left(cái\right)\)

Tổng số cái bánh được chia là 4+1=5(cái)

a; \(\dfrac{8}{9}\) + \(\dfrac{2}{6}\)  > \(\dfrac{5}{9}\) = \(\dfrac{3}{9}\) + \(\dfrac{2}{9}\)

Vậy \(\dfrac{8}{9}\) + \(\dfrac{2}{6}\) > \(\dfrac{3}{9}\) + \(\dfrac{2}{9}\)

b; \(\dfrac{11}{14}\) > \(\dfrac{10}{14}\) = \(\dfrac{5}{7}\)  = \(\dfrac{3}{7}\) + \(\dfrac{2}{7}\)

Vậy \(\dfrac{11}{14}\) > \(\dfrac{3}{7}\) + \(\dfrac{2}{7}\)

a, \(\dfrac{27}{45}+\dfrac{12}{30}=\dfrac{3}{5}+\dfrac{2}{5}=\dfrac{5}{5}=1\)

b, \(\dfrac{6}{18}+\dfrac{1}{3}=\dfrac{1}{3}+\dfrac{1}{3}=\dfrac{2}{3}\)

a) 27/45 + 12/30

= 3/5 + 2/5

= 5/5 =1.

b) 6/18 + 1/3

=1/3 + 1/3

= 2/3.

\(\dfrac{7}{8}:5\times\dfrac{1}{7}\\ =\dfrac{7}{8}\times\dfrac{1}{5}\times\dfrac{1}{7}\\ =\dfrac{7\times1\times1}{8\times5\times7}\\ =\dfrac{1}{8\times5}=\dfrac{1}{40}\)

a) x - 2/3 = 1/5 : 4/5

x - 2/3 = 1/5 × 5/4

x - 2/3 = 1/4

x = 1/4 + 2/3

x = 3/12 + 8/12

x = 11/12

b) x × 3/4 = 6/5

x = 6/5 : 3/4

x = 6/5 × 4/3

x = 24/15

x = 8/5

Câu 2a;

\(x\) - \(\dfrac{2}{3}\) = \(\dfrac{1}{5}\) : \(\dfrac{4}{5}\)

\(x\) - \(\dfrac{2}{3}\) = \(\dfrac{1}{4}\)

\(x\)       = \(\dfrac{1}{4}\) + \(\dfrac{2}{3}\)

\(x\)      = \(\dfrac{11}{12}\)