Đáp án:

12 + 24 + 88 + 76 + 10

= ( 12 + 88 )  + ( 24 + 76)

=       100         +       100

= 200

\(2\times169\times12-3\times68\times8-24\)

\(=24\times169-24\times68-24\)

\(=24\times\left(169-68-1\right)\)

\(=24\times100=2400\)

78 - 64 - 88 + 22 + 42 + 56

= 14 - 88 + 22 + 42 + 56

= -74 + 22 + 42 + 56

= -52 + 42 + 56

= -10 + 56

= 46

66 nhé

Kết Quả là 46

a, 56 x 12 + 24 x 36 + 24 x36 = 56 x 12 + 12 x 2 x 36 + 12 x 2 x 36

                                                   = 56 x 12 + 12 x 72 + 12 x 72

                                                   = 12 x ( 56 + 72 +  72 )

                                                   = 12 x 200

                                                     = 2400

b, 2005 x 178 - 77 x 2005 - 2005 = 2005 x ( 178 - 77 - 1 )

                                                          = 2005 x 100

                                                           = 200500

**** mình nha nguyễn thùy trang

0 

k nha

100 nhé !

=92-12*0                                                                                                                                                                                           =80                                     

rút gọn thành

1/2 x 2/3 x 3/4 x 4/5 x 5/6 x 6/7 x 7/8 x 8/9

1x2x3x4x5x6x7x8

__________________

2x3x4x5x6x7x8x9

gạch các số giống nhau ở tử và mẫu và bằng 1/9

56x24:12=56x2=112

56x24:3x8=56x24:24=56

63x18:9=63x2=126

24 x 55 + 12 x 88 + 24

= ( 24 x 55 ) + ( 12 x 88 ) + 24

= 1320 + 1056 + 24

= 2376 + 24

= 2400

_HT_

\(24\cdot55+12\cdot88+24\)

\(\Leftrightarrow\left(24\cdot55\right)+\left(24\cdot88:2\right)+24\)

\(\Rightarrow\left(24+55\right)+\left(24\cdot44\right)+24\)

\(\Leftrightarrow24\left(55+44+1\right)\)

\(\Leftrightarrow24\cdot100\)

\(\Leftrightarrow2400\)

a) \(\dfrac{3}{8}+\dfrac{7}{12}+\dfrac{10}{16}+\dfrac{10}{24}\)

\(=\dfrac{3}{8}+\dfrac{7}{12}+\dfrac{5}{8}+\dfrac{5}{12}\)

\(=\left(\dfrac{3}{8}+\dfrac{5}{8}\right)+\left(\dfrac{7}{12}+\dfrac{5}{12}\right)\)

\(=1+1\)

\(=2\)

b) \(\dfrac{4}{6}+\dfrac{7}{13}+\dfrac{17}{9}+\dfrac{19}{13}+\dfrac{1}{9}+\dfrac{14}{6}\)

\(=\dfrac{2}{3}+\dfrac{7}{13}+\dfrac{17}{9}+\dfrac{19}{13}+\dfrac{1}{9}+\dfrac{7}{3}\)

\(=\left(\dfrac{2}{3}+\dfrac{7}{3}\right)+\left(\dfrac{7}{13}+\dfrac{19}{13}\right)+\left(\dfrac{17}{9}+\dfrac{1}{9}\right)\)

\(=3+2+2\)

\(=7\)

c) \(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}\)

\(=\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+\dfrac{1}{4\cdot5}+\dfrac{1}{5\cdot6}+\dfrac{1}{6\cdot7}\)

\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{7}\)

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

\(=\dfrac{6}{7}\)