Phương pháp giải:

Thực hiện phép tính lần lượt theo thứ tự từ trái sang phải. 

Lời giải chi tiết:

a)

  2 × 3 × 1 = 6 × 1 = 6

  2 × 1 × 3 = 2 × 3 = 6

b)

  4 × 5 : 1 = 20 : 1 = 20

  4 : 1 × 5 = 4 × 5 = 20

c)

  8 : 4 × 1 = 2 × 1 = 2

  8 × 1 : 4 = 8 : 4 = 2

d)

  12 : 3 : 1 = 4 : 1 = 4

  12 : 1 : 3 = 12 : 3 = 4

Phương pháp giải:

Nhẩm lại bảng nhân, chia đã học rồi điền kết quả vào chỗ trống.

Lời giải chi tiết:

2 × 3 = 6          4 × 8 = 32

12 : 2 = 6         27 : 3 = 9

4 × 7 = 28        5 × 6 = 30

36 : 4 = 9         18 : 2 = 9

3 × 1 = 3          4 × 3 = 12

0 : 5 = 0           3 × 4 = 12

1 × 8 = 8          12 : 4 = 3

0 : 3 = 0           12 : 3 = 4

a: \(=\dfrac{-5}{8}+\dfrac{7}{12}=\dfrac{-15}{24}+\dfrac{14}{24}=\dfrac{-1}{24}\)

b: \(=\dfrac{3}{4}-\dfrac{5}{6}+\dfrac{11}{12}=\dfrac{9}{12}-\dfrac{10}{12}+\dfrac{11}{12}=\dfrac{10}{12}=\dfrac{5}{6}\)

c: \(=\dfrac{6}{36}-\dfrac{1}{36}=\dfrac{5}{36}\)

d: \(=\dfrac{5}{12}+\dfrac{5}{12}=\dfrac{10}{12}=\dfrac{5}{6}\)

e: \(=\dfrac{-8}{56}-\dfrac{7}{56}=\dfrac{-15}{56}\)

f: \(=\dfrac{-5}{15}+\dfrac{3}{25}=\dfrac{-25}{75}+\dfrac{9}{75}=\dfrac{-16}{75}\)

a. 

\(\left(1\frac{1}{4}+\frac{3}{5}\right):\left(-\frac{11}{12}\right)+\left(\frac{3}{8}-1\frac{2}{5}\right):\left(-\frac{11}{12}\right)\) 

\(=\left(\frac{5}{4}+\frac{3}{5}+\frac{3}{8}-\frac{7}{5}\right):\left(-\frac{11}{12}\right)\)  

\(=\left(\frac{13}{8}-\frac{4}{5}\right):\left(-\frac{11}{12}\right)\) 

\(=\frac{33}{40}:\left(-\frac{11}{12}\right)\) 

\(=\frac{33}{40}\cdot\left(-\frac{12}{11}\right)\) 

\(=\frac{-9}{10}\)  

b. 

\(\left(\frac{3}{8}-1\frac{2}{5}\right):\left(-\frac{11}{15}\right)+\left(1\frac{1}{4}+\frac{3}{5}\right):\left(-\frac{11}{15}\right)\) 

\(=\left(\frac{3}{8}-\frac{7}{5}+\frac{5}{4}+\frac{3}{5}\right):\left(-\frac{11}{15}\right)\)  

\(=\left(\frac{13}{8}-\frac{4}{5}\right):\left(-\frac{11}{15}\right)\) 

\(=\frac{33}{40}:\left(-\frac{11}{15}\right)\) 

\(=\frac{33}{40}\cdot\left(-\frac{15}{11}\right)\) 

\(=\frac{-9}{8}\)

a) 2/9 - (1/20 + 2/9)

= 2/9 - 1/20 - 2/9

= (2/9 - 2/9) - 1/20

= 0 - 1/20

= -1/20

b) -3/14 + 2/13 + (-25/14) + (-15/13)

= (-3/14 - 25/14) + (2/13 - 15/13)

= -2 - 1

= -3

c) -3/11 + 11/8 - 3/8 + (-8/11)

= (-3/11 - 8/11) + (11/8 - 3/8)

= -1 + 1

= 0

d) 3/8 + (-1/4) - (7/12 - 1/6)

= 1/8 - 5/12

= -7/24

e) (1/3 + 12/67 + 13/41) - (79/67 - 28/41)

= 1/3 + 12/67 + 13/41 - 79/67 + 28/41

= 1/3 + (12/67 - 79/67) + (13/41 + 28/41)

= 1/3 - 1 + 1

= 1/3

\(A=\frac{3}{7}+\frac{4}{9}+\frac{4}{7}+\frac{7}{11}\)

\(A=1+\frac{4}{9}+\frac{7}{11}\)

\(A==\frac{76}{33}\)

\(B=\frac{1}{8}+\frac{1}{12}+\frac{3}{8}+\frac{5}{12}\)

\(B=\frac{1}{2}+\frac{1}{2}\)

\(B=\frac{1}{4}\)

1)     \(\frac{1}{12}+\frac{1}{16}+\frac{3}{4}\)

\(=\frac{4}{48}+\frac{3}{48}+\frac{36}{48}\)

\(=\frac{4+3+36}{48}\)

\(=\frac{43}{48}\)

2)   a)    \(\frac{1}{15}+\frac{4}{15}+\frac{5}{18}+\frac{7}{18}\)

\(=\left(\frac{1}{15}+\frac{4}{15}\right)+\left(\frac{5}{18}+\frac{7}{18}\right)\)

\(=\frac{1}{3}+\frac{2}{3}=1\)

b)    \(\frac{1}{8}+\frac{1}{12}+\frac{3}{8}+\frac{5}{12}\)

\(=\left(\frac{1}{8}+\frac{3}{8}\right)+\left(\frac{1}{12}+\frac{5}{12}\right)\)

\(=\frac{1}{2}+\frac{1}{2}=1\)

\(\dfrac{18}{3}=18:3=6\)

\(\dfrac{45}{9}=45:9=5\)

\(\dfrac{8}{8}=8:8=1\)

\(\dfrac{7}{1}=7:1=7\)

`1/3 + 5/4`

`= 4/12 + 15/12`

`= 19/12

__

`4/12 - 1/15`

`= 1/3 -1/15`

`= 5/15 -1/15`

`=4/15`

__

`2/3 xx 15/8`

`= (2xx15)/(3xx88)`

`= 30/24`

`=5/4`

__

`2/3 : 8/21`

`= 2/3 xx 21/8`

`= (2xx21)/(3xx8)`

`= 42/24`

`=7/4`

1/3+5/4=4/12+15/12

=19/12

4/12-1/15=20/60-4/60

=16/60=4/15

2/3x15/8=30/24=5/4

2/3:8/21=42/24=7/4

nhớ cho a tích nhé =)) a bị bịp nhiều rồi

\(\dfrac{1}{3}+\dfrac{5}{4}=\dfrac{4}{12}+\dfrac{15}{12}=\dfrac{19}{12}\)

_____________________________\(\dfrac{4}{12}-\dfrac{1}{15}=\dfrac{60}{180}-\dfrac{12}{180}=\dfrac{48}{180}=\dfrac{4}{15}\)

_____________________________

\(\dfrac{2}{3}\)x\(\dfrac{15}{8}\)\(=\dfrac{30}{24}=\dfrac{5}{4}\)

_____________________________

\(\dfrac{2}{3}:\dfrac{8}{21}=\dfrac{2}{3}\)x\(\dfrac{21}{8}=\)\(\dfrac{42}{24}=\dfrac{7}{4}\)

Chúc bạn học tốt:>

a) 1 + 1/4 + 1/8 + 1/16

= 16/16 + 4/16 + 2/16 + 1/16

= 23/16

b) 2 - 1/8 - 1/12 - 1/16

= 96/48 - 6/46 - 4/48 - 3/48

= 83/48

c) 4/99 × 18/5 : 12/11 + 3/5

= 8/55 : 12/11 + 3/5

= 2/15 + 3/5

= 2/15 + 9/15

= 11/15

d) (1 - 3/4) × (1 + 1/3) : (1 - 1/3)

= 1/4 × 4/3 : 2/3

= 1/3 : 2/3

= 2

1 + 1/4 + 1/8 + 1/16

= 16 + 4 + 2 + 1 / 16

=23/16

2-1/8-1/12-1/16

= 96 - 6 - 4 - 3 / 48

= 83 / 48

4/99 x 18/5 : 12 /11 + 3/5

= 4/99 x 18/5 x 11/12 + 3/5

= 2/15 + 3/5

= 11/15

(1 - 3/4) x (1+1/3) : (1-1/3) 

= 1/4 x 4/3 : 2/3

= 1/4 x 4/3 x 3/2

= 1/2