![](https://rs.olm.vn/images/avt/0.png?1311)
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20
=(1+19)+(2+18)+(3+17)+(4+16)+(5+15)+(6+14)+(7+13)+(8+12)+(9+11)+20+10
=20+20+20+20+20+20+20+20+20+20+10
=20×10+10
=200+10
=210
= ( 1 + 19 ) + ( 2 + 18 ) + ( 3 + 17 ) + (4 + 16 ) + ( 5 + 15 ) + ( 6 + 14 ) + ( 7 + 13 ) + ( 8 + 12) + ( 9+ 11 ) + 20
= 20 + 20 + 20 +20 + 20 +20 + 20 + 20 + 20 +20
= 20 x 10
= 200
tui đầu tiên đó
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 18/15 + 7/15 + 12/15 =18/15 + 12/15 + 7/15
= 30/15 + 7/15
= 37/15
b) 9/7 + 8/7 +11/7 = 9/7 + 11/7 + 8/7
= 20/7 + 8/7 = 28/7 nha . tk mk nhé b
![](https://rs.olm.vn/images/avt/0.png?1311)
a,18/15+7/15+12/15=18+7+12/15
=37/15
b,9/7+8/7+11/7=9+8+11/7
=28/7=1/4
+8/15 + 7/15 +12/15 = (18+7+12)/7 = [(18+12)+7]/15= (30+7)/15=37/15=7/3
9/7 + 8/7 + 11/7 = (9+8+11)/7= [(9+11)+8]/7=(20+8)/7= 28/7 =4
![](https://rs.olm.vn/images/avt/0.png?1311)
(20+10)-(11+19)+(12+18)-(13+17)+(14+16)-15
=30-30+30-30-15+30
=15
10-11+12-13+14-15+16-17+18-19+20
= (10+20)+(-11-19)+(12+18)+(-13-17)+(14+16)-15
= 30-30+30-30+30-15
= 15
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\frac{18}{15}+\frac{7}{15}+\frac{12}{15}\)
= \(\frac{18+7+12}{15}\)
= \(\frac{37}{15}\)
b) \(\frac{9}{7}+\frac{8}{7}+\frac{11}{7}\)
= \(\frac{9+8+11}{7}\)
= \(\frac{28}{7}\)
a) 18/15 + 7/15 + 12/15
= (18/15 + 12/15) + 7/15
= 30/15 + 7/15
= 37/15
b) 9/7 + 8/7 + 11/7
= (9/7 + 11/7) + 8/7
= 20/7 + 8/7
= 28/7
chuc ban hok tot
![](https://rs.olm.vn/images/avt/0.png?1311)
a.\(\dfrac{18}{15}+\dfrac{7}{15}+\dfrac{12}{15}=\dfrac{18+7+12}{15}=\dfrac{37}{15}\)
b.\(\dfrac{9}{7}+\dfrac{8}{7}+\dfrac{11}{7}=\dfrac{9+8+11}{7}=\dfrac{28}{7}=4\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Tính bằng cách thuận tiện nhất:
9/4 x 15/11 + 3/4 : 11/7 - 3/4 x 8/11
[Lưu ý trình bày cách làm ra!]
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{9}{4}\times\dfrac{15}{11}+\dfrac{3}{4}:\dfrac{11}{7}-\dfrac{3}{4}\times\dfrac{8}{11}\)
\(=\dfrac{3}{4}\times3\times\dfrac{15}{11}+\dfrac{3}{4}\times\dfrac{7}{11}-\dfrac{3}{4}\times\dfrac{8}{11}\)
\(=\dfrac{3}{4}\times\dfrac{45}{11}+\dfrac{3}{4}\times\dfrac{7}{11}-\dfrac{3}{4}\times\dfrac{8}{11}\)
\(=\dfrac{3}{4}\times\left(\dfrac{45}{11}+\dfrac{7}{11}-\dfrac{8}{11}\right)\)
\(=\dfrac{3}{4}\times4\)
\(=3\)
`9/4xx15/11+3/4:11/7-3/4xx8/11`
`=3/4xx15/11xx3+3/4xx7/11-3/4xx8/11`
`=3/4xx45/11+3/4xx7/11-3/4xx8/11`
`=3/4xx(45/11+7/11-8/11)`
`=3/4xx4`
`=3`
\(=\frac{10}{11}-\frac{3}{7}:\frac{7}{15}:\frac{15}{14}\)
\(=\frac{10}{11}-\frac{45}{49}:\frac{15}{14}\)
\(=\frac{10}{11}-\frac{6}{7}=\frac{70}{77}-\frac{66}{77}=\frac{4}{77}\)