a) \(\frac{5}{1.4}+\frac{5}{4.7}+\frac{5}{7.10}+.....+\frac{5}{27.30}\)

\(=\frac{5}{3}\left(\frac{1}{1.4}+\frac{1}{4.7}+........+\frac{1}{27.30}\right)\)

\(=\frac{5}{3}\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+.....+\frac{1}{27}-\frac{1}{30}\right)\)

\(=\frac{5}{3}\left(1-\frac{1}{30}\right)\)

\(=\frac{5}{3}.\frac{29}{30}=\frac{29}{36}\)

Đặt \(A=\frac{12}{3\cdot5}+\frac{12}{5\cdot7}+\frac{12}{7\cdot9}+....+\frac{12}{97\cdot99}\)

\(2A=\frac{12}{3}-\frac{12}{5}+\frac{12}{5}-\frac{12}{7}+...+\frac{12}{97}-\frac{12}{99}\)

\(2A=\frac{12}{3}-\frac{12}{99}\)

\(A=\frac{128}{33}\cdot\frac{1}{2}=\frac{64}{33}\)

a)\(\frac{5}{12}:\frac{2}{5}+\frac{7}{12}:\frac{2}{5}-\frac{1}{3}:\frac{2}{5}=\left(\frac{5}{12}+\frac{7}{12}-\frac{1}{3}\right):\frac{2}{5}=\frac{2}{3}:\frac{2}{5}=\frac{5}{3}.\)

b) \(\left(6,7+2,3+5,8\right):1,2=14,8:1,2=\frac{148}{10}:\frac{12}{10}=\frac{148}{12}=\frac{74}{6}=\frac{37}{3}\)

hk tốt!

=25/24 + 35/24 - 5/6

=60/24 - 5/6

=15/6 - 5/6

=15-5/6

=10/6

=5/3

mình chỉ biết í a thôi

a) 2/9 +1/5 +7/9+4/5

=( 2/9+7/9)+(1/5+4/5)

=1+1=2

b) 1/12+3/16+5/12+5/16

=(1/12 +5/12)+(3/16+5/16)

=1/2 +1/2=1

8+11=19

hoac = 176

\(=66\frac{5}{12}+37+25\frac{1}{2}\)

\(\frac{797}{12}+\frac{444}{12}+\frac{51}{2}=\frac{1241}{12}+\frac{306}{12}=\frac{1547}{12}=128\frac{11}{12}\)

**** **** ****

\(66\frac{5}{12}+36\frac{12}{12}+25\frac{12}{24}=66\frac{5}{12}+36+1+25\frac{6}{12}=\left(66+37+25\right)+\left(\frac{5}{12}+\frac{6}{12}\right)=128+\frac{11}{12}=128\frac{11}{12}\)

Dễ mà  

Tự nghĩ đi bn

============= 

3 chữ

thử đoán xem

7/12-2/7+1/12=7/12+1/12-2/7=8/12-2/7=2/3+2/7=14/21+6/21=20/21

12/17-5/17-4/17=3/17

Trả lời

4/5+12/15+1/2.7

=4/5+12/15+7/2

=24/15+7/2

=8/5+7/2

=51/10.

\(\frac{4}{5}+\frac{12}{15}+\frac{5}{10}\times7\)

\(=\frac{4}{5}+\frac{4}{5}+\frac{7}{2}\)

\(=\frac{8}{5}+\frac{7}{2}\)

\(=\frac{16}{10}+\frac{35}{10}\)

\(=\frac{51}{10}\)

~Study well~

#KSJ

\(\frac{4}{5}+\frac{1}{5}=\frac{5}{5}=1\)
\(\frac{14}{12}+\frac{2}{3}=\frac{14}{12}+\frac{8}{12}=\frac{22}{12}=1\frac{10}{12}\)
4/5 + 1/5
= 5/5
= 1

14/12 + 2/3
= 14/12 + 8/12
= 22/12

4/5 + 1/5
= 5/5
= 1

14/12 + 2/3
= 14/12 + 8/12
= 22/12

1 hoặc 5/5

11/6

nha bn

k mk nha bn

ở giữa là j v bro

bạn ơi cho mình hỏi cái chỗ 3/5 9/12 là dấu nhân hay dấu gì