Bài giải :

Số các số hạng của dãy số trên là :

( 34 - 1 ) : 1 + 1 = 34 ( số hạng )

Tổng dãy số trên là :

( 34 + 1 ) x 34 : 2 = 578

Đáp số : 578

(6:3/5-7/6×6/7) : (21/5×10/11+57/11)

=(10-1):(42/11+57/11)

=9:9

=1

(6:3/5-7/6x6/7):(21/5x10/11+57/11)

= (10-1):(42/11+57/11)

=9:9

=1

~~~~ Hoc tot ~~~~~

8757577

3/4+1/2+5/8=15/8

5/9+9/8-15/28=577/504

11/30-9/25x15/27=1/6

3/4:5/8:3/10=4

10/11+9/10 = 199/110

15/30+7/30 = 11/15

1/2+1/3 = 5/6

3/5+11/15 = 4/3

3/4+1/6 = 11/12

5/11+4/11 = 9/11

BẠN THẬT XUẤT SẮC 

CẢM ƠN BẠN NHA

CHÚC BAN CUỐI TUẦN VUI VẺ

`1/2+2/4+3/6+4/8+5/10+6/12`

`=1/2+1/2+1/2+1/2+1/2+1/2`

`=1/2*6=3`

`1/3+1/4+1/5+8/10+20/15+20/30`

`=(1/3+1/4)+(1/5+4/5)+(4/3+2/3)`

`=7/12+1+2`

`=7/12+3=43/12`

\(\dfrac{1}{2}+\dfrac{2}{4}+\dfrac{3}{6}+\dfrac{4}{8}+\dfrac{5}{10}+\dfrac{6}{12}\)
\(=\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}\)
\(=\dfrac{1}{2}\times6=3\)
\(------\)
\(\dfrac{1}{3}+\dfrac{1}{4}+\dfrac{1}{5}+\dfrac{8}{10}+\dfrac{20}{15}+\dfrac{20}{30}\)
\(=\dfrac{1}{3}+\dfrac{1}{4}+\dfrac{1}{5}+\dfrac{4}{5}+\dfrac{4}{3}+\dfrac{2}{3}\)
\(=\left(\dfrac{1}{3}+\dfrac{4}{3}+\dfrac{2}{3}\right)+\left(\dfrac{1}{5}+\dfrac{4}{5}\right)+\dfrac{1}{4}\)
\(=\dfrac{7}{3}+1+\dfrac{1}{4}\)
\(=\dfrac{28}{12}+\dfrac{12}{12}+\dfrac{3}{12}\)
\(=\dfrac{43}{12}\)

Giải chi tiết cho mình nha

2/5 + 11/15 = 17/15
7/8 - 7/9 = 7/72
11/13 x 26/31 = 22/31
16/24 : 4 = 1/6
30 : 6/5 = 25
9/16 : 4 = 9/64
1/2 : 1/3 x 8/15 = 3/2 x 8/15 = 4/5

Hướng dẫn giải:

a) 3 x (20 – 5)

Cách 1:

3 x (20 – 5) = 3 x 15 = 45

Cách 2:

3 x (20 – 5) = 3 x 20 – 3 x 5 = 60 – 15 = 45

b) 20 x (40 – 1)

Cách 1:

20 x (40 – 1) = 20 x 39 = 780

Cách 2:

20 x (40 – 1) = 20 x 40 – 20 x 1 = 800 – 20 = 780

^{1/2 + 2/3 - 3/4 * 4/5 * 5/6 * 6/7 * 7/8 * 8/9 *...* 29/30 : 6/10}

^{= 1/2 + 2/3 - 1/10 : 6/10}

^{= 1/2 + 2/3 - 1/6}

^{= 1}

1/2 + 3/6 + 5/10 + 7/14 + 9/18 + 11/22

= 1/2 + ( 3/6=1/2) + (5/10=1/2) + (7/14 = 1/2) +( 9/18 =1/2) + (11/22 = 1/2)

= 1/2 + 1/2 + 1/2 + 1/2 + 1/2 + 1/2

= 1 + 1 + 1

= 3