\(\frac{13}{90}\)+ \(\frac{1}{4}\)+ \(\frac{77}{90}\)

= \(\left(\frac{13}{90}+\frac{77}{90}\right)+\frac{1}{4}\)

= 1 + \(\frac{1}{4}\)

= \(\frac{5}{4}\)

a )  13/90 + 1/4 + 77/90                                       

= ( 13/90 + 77/90 ) + 1/4 

=   90/90 + 1/4 

= 1 + 1/4 

= 5/4 

b )        16/81 + 5/13 + 65/ 81 + 8/13 

       =  ( 16/81 + 65/81 ) + ( 5/13+8/13 ) 

       =           81/81         + 13/13 

       =             1 + 1 

       =  2 

Chắc 100% 

cảm ơn các bạn nha

a) Số các số hạng trong A là: \(\left(25-1\right):1+1=25\) (số)

Tổng A bằng: \(\left(25+1\right)\cdot25:2=325\)

b) Số các số hạng trong B là: \(\left(50-2\right):2+1=25\) (số)

Tổng B bằng: \(\left(50+2\right)\cdot25:2=650\)

c) Số các số hạng trong C là: \(\left(81-1\right):4+1=21\) (số)

Tổng C bằng: \(\left(81+1\right)\cdot21:2=861\)

#Urushi

a)= ( 81 , 6 x 27 , 3 – 17 , 3 x 81 , 6 ) x 0

=0 ( vì 0 nhân với số nào cũng bằng 0)

b)= ( 13 , 75 – 0 , 48 x 5 ) x ( 42 , 75 : 3 + 2 , 9 ) x ( 9-9)

= ( 13 , 75 – 0 , 48 x 5 ) x ( 42 , 75 : 3 + 2 , 9 ) x 0

= 0 ( vì 0 nhân với số nào cũng bằng 0)

c)=( 792 , 81 x 0 , 25 + 792 , 81 x 0 , 75 ) x 0

=0 ( vì 0 nhân với số nào cũng bằng 0 )

a ) ( 81 , 6 x 27 , 3 – 17 , 3 x 81 , 6 ) x ( 32 x 11 - 3200 x 0 , 1 - 32 )

= ( 81 , 6 x 27 , 3 – 17 , 3 x 81 , 6 ) x ( 352 - 320 - 32 )

= ( 81 , 6 x 27 , 3 – 17 , 3 x 81 , 6 ) x 0

= 0.

b ) ( 13 , 75 – 0 , 48 x 5 ) x ( 42 , 75 : 3 + 2 , 9 ) x ( 1 , 8 x 5 – 0 , 9 x 10 )

= ( 13 , 75 – 0 , 48 x 5 ) x ( 42 , 75 : 3 + 2 , 9 ) x ( 9 - 9 )

= ( 13 , 75 – 0 , 48 x 5 ) x ( 42 , 75 : 3 + 2 , 9 ) x 0

= 0

c ) ( 792 , 81 x 0 , 25 + 792 , 81 x 0 , 75 ) x ( 11 x 9 – 900 x 0 , 1 – 9 )

= ( 792 , 81 x 0 , 25 + 792 , 81 x 0 , 75 ) x ( 99 - 90 - 9 )

= ( 792 , 81 x 0 , 25 + 792 , 81 x 0 , 75 ) x 0

= 0.

Hok tốt !

a)32 x 11 -3200x 0,1 -32

=32x11-32x100x0,1-32

=32x(11-10-1)=32x0=0

nên(81,6x27,3-17,3x81,6)x(32x11-3200x0,1-32)

=(81,6x27,3-17,3x81,6)x0

=0

b)1,8x5 -0,9x10=1,8x5-0,9x2x5

=1,8x5-1,8x5

=0

nên (13,75-0,48 x 5)x(42,75:3+2,9)x(1,8x5-0,9x10)=0

c)(792,81x0,25+792,81x0,75)x(11x9-900x0,1-9)

=792,81x(0,25+0,75)x(99-90-9)

=792,81x1x0

=0

Ta lấy 77 là Mẫu số chung

= 77 nhân (1111 - 99 + 4 - 4 + 98 - 100 + 93 - 81 - 12)

= 77 nhân 10

=770

nhầm. Thừa số chung

KHO THE

\(A=\frac{\left[\left(25-1\right):1+1\right]\left(25+1\right)}{2}=325.\)

\(B=\frac{\left[\left(51-3\right):2+1\right]\left(51+3\right)}{2}=675\)

\(C=\frac{\left[\left(81-1\right):4+1\right]\left(81+1\right)}{2}=861\)

Sai môn rồi

a,(815+185)-(23+77)

=1000-100=900

b,(2496+7504)+(5347+4653)+3145

=10000+               10000          +3145

=23146

c,(1+19)+(3+17)+(5+15)+(7+13)+(9+11)

=20+20+20+20+20=100

d,(52+28)+(37+63)-(42+38)

=80+100-80=100

mk nha

a,(815+185)-(23+77)

=1000-100=900

b,(2496+7504)+(5347+4653)+3145

=10000+               10000          +3145

=23146

c,(1+19)+(3+17)+(5+15)+(7+13)+(9+11)

=20+20+20+20+20=100

d,(52+28)+(37+63)-(42+38)

=80+100-80=100

mk nha

Tính nhanh:

a. 815 - 23 - 77 + 185

= (815+185)-(23+77)

=1000 - 100

= 900

b. 3145 + 2496 + 5347 + 7504 + 4653

=3145+(2496+7504)+(5347+4653)

= 3145+10 000 + 10 000

= 3145 + 20 000

= 23 145

c. 1 + 3 + 5 + 7 + 9+ 11 + 13 + 15 + 17 + 19

=(1+19)+(3+17)+(5+15)+(7+13)+(9+11)

= 20  +   20    +   20 + 20 + 20

= 20 × 5 

= 100

d. 52 - 42 + 37 + 28 - 38 + 63

= ( 52 + 28 ) - ( 42 + 38 ) + ( 37 + 63 )

=  80  -  80  + 100

= 0 + 100

= 100 

Bài 1: 

\(A=\frac{24.47-22}{24+47.23}.\frac{5+\frac{5}{7}+\frac{5}{11}-\frac{5}{13}+\frac{5}{1001}}{6+\frac{6}{7}+\frac{6}{11}-\frac{6}{13}+\frac{6}{1001}}\)\(=\frac{47.23+47-22}{24.47.23}.\frac{5\left(1+\frac{1}{7}+\frac{1}{11.}-\frac{1}{13}+\frac{1}{1001}\right)}{6\left(1+\frac{1}{7}+\frac{1}{11}-\frac{1}{13}+\frac{1}{1001}\right)}\) 

                                                                         \(=\frac{47.23+24}{24+47.23}.\frac{5}{6}\) 

                                                                         \(=1.\frac{5}{6}=\frac{5}{6}\) 

Bài 2: 

\(81^7-27^9-9^{13}=\left(3^4\right)^7-\left(3^3\right)^9-\left(3^2\right)^{13}\) 

                                      \(=3^{28}-3^{27}-3^{26}\) 

                                      \(=3^{22}\left(3^6-3^5-3^4\right)\) 

                                      \(=3^{22}.405\) chia hết cho 405 

 =>đpcm

\(1,-\dfrac{4}{7}+\dfrac{2}{3}\times\dfrac{-9}{14}\)

\(=\dfrac{-4}{7}+\dfrac{-18}{42}\)

\(=\dfrac{-4\times6}{7\times6}+\dfrac{-18}{42}\)

\(=\dfrac{-20}{42}+\dfrac{-18}{42}\)

\(=-\dfrac{38}{42}\)

\(=-\dfrac{19}{21}\)

\(2,\dfrac{17}{13}-\left(\dfrac{4}{13}-11\right)\)

\(=\dfrac{17}{13}-\dfrac{4}{13}+11\)

\(=\dfrac{13}{13}+11\)

\(=1+11\)

\(=12\)

\(3,8\dfrac{2}{7}-\left(3\dfrac{4}{9}+4\dfrac{2}{7}\right)\)

\(=\dfrac{58}{7}-\left(\dfrac{31}{9}+\dfrac{30}{7}\right)\)

\(=\dfrac{58}{7}-\dfrac{31}{9}-\dfrac{30}{7}\)

\(=\dfrac{58}{7}-\dfrac{30}{7}-\dfrac{31}{9}\)

\(=\dfrac{28}{7}-\dfrac{31}{9}\)

\(=\dfrac{28\times9}{7\times9}-\dfrac{31\times7}{9\times7}\)

\(=\dfrac{252}{63}-\dfrac{217}{63}\)

\(=\dfrac{35}{63}\)

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

\(5,\left(\dfrac{2}{3}-1\dfrac{1}{2}\right):\dfrac{4}{3}+\dfrac{1}{2}\)

\(=\left(\dfrac{2}{3}-\dfrac{3}{2}\right):\dfrac{4}{3}+\dfrac{1}{2}\)

\(=\left(\dfrac{2\times2}{3\times2}-\dfrac{3\times3}{2\times3}\right):\dfrac{4}{3}+\dfrac{1}{2}\)

\(=\left(\dfrac{4}{6}-\dfrac{9}{6}\right):\dfrac{4}{3}+\dfrac{1}{2}\)

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

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

\(=\dfrac{-15}{24}+\dfrac{1}{2}\)

\(=\dfrac{-15}{24}+\dfrac{1\times12}{2\times12}\)

\(=\dfrac{-15}{24}+\dfrac{12}{24}\)

\(=\dfrac{-3}{24}\)

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

\(6,\dfrac{-5}{13}+\dfrac{2}{5}+\dfrac{-8}{13}+\dfrac{3}{5}-\dfrac{3}{7}\)

\(=\left(\dfrac{-5}{13}+\dfrac{-8}{13}\right)+\left(\dfrac{2}{5}+\dfrac{3}{5}\right)-\dfrac{3}{7}\)

\(=\dfrac{-13}{13}+\dfrac{5}{5}-\dfrac{3}{7}\)

\(=-1+1-\dfrac{3}{7}\)

\(=-\dfrac{3}{7}\)

\(7,\dfrac{6}{5}\times\dfrac{3}{7}+\dfrac{6}{5}:\dfrac{7}{10}+\dfrac{6}{5}\)

\(=\dfrac{6}{5}\times\dfrac{3}{7}+\dfrac{6}{5}\times\dfrac{10}{7}+\dfrac{6}{5}\)

\(=\dfrac{6}{5}\times\left(\dfrac{3}{7}+\dfrac{10}{7}+1\right)\)

\(=\dfrac{6}{5}\times\left(\dfrac{3}{7}+\dfrac{10}{7}+\dfrac{1\times7}{1\times7}\right)\)

\(=\dfrac{6}{5}\times\left(\dfrac{3}{7}+\dfrac{10}{7}+\dfrac{7}{7}\right)\)

\(=\dfrac{6}{5}\times\dfrac{20}{7}\)

\(=\dfrac{120}{35}\)

\(=\dfrac{24}{7}\)