ảnh 1 : tr 123 SGK TOÁN 4

ảnh 2 mình ko biết 

Sau khi chuyển thì tổng số dầu hai thùng không đổi. 

Sau khi chuyển nếu số dầu thùng M là \(5\)phần thì số dầu thùng N là \(4\)phần.

Tổng số phần bằng nhau là: 

\(5+4=9\)(phần) 

Số dầu thùng M sau khi chuyển là: 

\(45\div9\times5=25\left(l\right)\)

Số dầu thùng M là: 

\(25-9=16\left(l\right)\)

Số dầu thùng N là: 

\(45-16=29\left(l\right)\)

câu trả lời là 3,9

2,3 

+

 1,6

-------

3.9

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\(A=\frac{1}{2}+\frac{5}{6}+\frac{11}{12}+\frac{19}{20}+\frac{29}{30}+\frac{41}{42}+\frac{55}{56}+\frac{71}{72}\)

\(=1-\frac{1}{2}+1-\frac{1}{6}+1-\frac{1}{12}+1-\frac{1}{20}+1-\frac{1}{30}+1-\frac{1}{42}+1-\frac{1}{56}+1-\frac{1}{72}\)

\(=8-\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}\right)\)

\(=8-\left(\frac{1}{1\times2}+\frac{1}{2\times3}+\frac{1}{3\times4}+\frac{1}{4\times5}+\frac{1}{5\times6}+\frac{1}{6\times7}+\frac{1}{7\times8}+\frac{1}{8\times9}\right)\)

\(=8-\left(\frac{2-1}{1\times2}+\frac{3-2}{2\times3}+\frac{4-3}{3\times4}+\frac{5-4}{4\times5}+\frac{6-5}{5\times6}+\frac{7-6}{6\times7}+\frac{8-7}{7\times8}+\frac{9-8}{8\times9}\right)\)

\(=8-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}\right)\)

\(=8-\left(1-\frac{1}{9}\right)\)

\(=\frac{64}{9}\)

\(B=\frac{2}{3}+\frac{8}{9}+\frac{26}{27}+\frac{80}{81}+\frac{242}{243}\)

\(=1-\frac{1}{3}+1-\frac{1}{9}+1-\frac{1}{27}+1-\frac{1}{81}+1-\frac{1}{243}\)

\(=5-\left(\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81}+\frac{1}{243}\right)\)

\(C=\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81}+\frac{1}{243}\)

\(3\times C=1+\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81}\)

\(3\times C-C=\left(1+\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81}\right)-\left(\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81}+\frac{1}{243}\right)\)

\(2\times C=1-\frac{1}{243}\)

\(C=\frac{121}{243}\)

\(B=5-C=5-\frac{121}{243}=\frac{1094}{243}\)

20338 + 567887 - 222 + 334 = 588337

23456 + 76543 - 8765 = 91234 

cảm ơn Phùng Minh Hằng rất nhiều 

\(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{9900}\)

\(=\frac{1}{1\times2}+\frac{1}{2\times3}+\frac{1}{3\times4}+\frac{1}{4\times5}+...+\frac{1}{99\times100}\)

\(=\frac{2-1}{1\times2}+\frac{3-2}{2\times3}+\frac{4-3}{3\times4}+\frac{5-4}{4\times5}+...+\frac{100-99}{99\times100}\)

\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{99}-\frac{1}{100}\)

\(=1-\frac{1}{100}=\frac{99}{100}\)

A = 1/2 + 1/6 + 1/12 + 1/20 + ......+1/9900

A = 1/1x2 + 1/2x3 + 1/3x4 + 1/4x5 + ... + 1/99x100

A = 1 -1/2 + 1/2 - 1/3 + 1/3 -1/4 + 1/4-1/5 + ... + 1/99- 1/100

A = 1 + (-1/2 + 1/2) + (-1/3 + 1/3) + (-1/4+ 1/4) + .... + (-1/99 + 1/99) - 1/100

A = 1 -  1/100

A = 100/100 - 1/100

A = 99/100

a) \(\frac{18}{15}+\frac{7}{15}+\frac{12}{15}\)

\(=\left(\frac{18}{15}+\frac{12}{5}\right)+\frac{7}{15}\)

\(=6+\frac{7}{15}\)

\(=\frac{97}{15}\)

b) \(\frac{9}{7}+\frac{8}{7}+\frac{11}{7}\)

\(=\frac{17}{7}+\frac{11}{7}\)

\(=\frac{28}{7}=4\)

TL

a) \(\frac{18}{15}+\frac{7}{15}+\frac{12}{15}\)\(=\frac{97}{15}\)

b) \(\frac{9}{7}+\frac{8}{7}+\frac{11}{7}\)\(=4\)

nha bn

HT

Số cam Nam ăn bằng số phần quả cam là : 

\(1+\frac{1}{6}=\frac{7}{6}\text{ quả cam}\)

7/6 nhé.k đi ah

\(\dfrac{6}{9}\)\(\times\dfrac{2}{8}\)=\(\dfrac{2}{3}\times\dfrac{1}{4}\)

         \(=\)\(\dfrac{1}{6}\)

tick mình nhé

= 1/6 

k cho mk nha

HT

=59/18 nha

59/18