Tính bằng 2 cách :

a). 234 x 25 + 234 x 75 

C1: \(234\times25+234\times75\)

\(=5850+17550\)

\(=23400\)

C2: \(234\times25+234\times75\)

\(=234\times\left(25+75\right)\)

\(=234\times100\)

\(=23400\)

b). 765 x 123 - 755 x 23

C1: \(765\times123-765\times23\)

\(=94095-17595\)

\(=76500\)

C2: \(765\times123-765\times23\)

\(=765\times\left(123-23\right)\)

\(=765\times100\)

\(=76500\)

=> Bạn xem lại đề ạ!

c). 476 x ( 45 + 55 )

C1: \(476\times\left(45+55\right)\)

\(=476\times100\)

\(=47600\)

C2: \(476\times\left(45+55\right)\)

\(=476\times45+476\times55\)

\(=21420+26180\)

\(=47600\)

d). 2415 : 5 : 5

=> Xem lại đề ạ

e). ( 76 x 28 ) : 7

C1: \(\left(76\times28\right)\div7\)

\(=2128\div7\)

\(=304\)

C2: \(\left(76\times28\right)\div7\)

\(=76\times\left(28\div7\right)\)

\(=76\times4\)

\(=304\)

g). ( 175 + 29070 ) : 5

C1: \(\left(175+29070\right)\div5\)

\(=29245\div5\)

\(=5849\)

C2: \(\left(175+29070\right)\div5\)

\(=175\div5+29070\div5\)

\(=35+5814\)

\(=5849\)

h). ( 3224 - 1236 ) : 4

C1: \(\left(3224-1236\right)\div4\)

\(=1988\div4\)

\(=497\)

C2: \(\left(3224-1236\right)\div4\)

\(=3224\div4-1236\div4\)

\(=806-309\)

\(=497\)

          Bài 1:

Rút gọn các phân số sau: 

\(\dfrac{12}{24}\) = \(\dfrac{12:12}{24:12}\) = \(\dfrac{1}{2}\)

\(\dfrac{120}{90}\) = \(\dfrac{120:30}{90:30}\) = \(\dfrac{4}{3}\)

\(\dfrac{42}{24}\) = \(\dfrac{42:6}{24:6}\) = \(\dfrac{7}{4}\)

          Bài 2:

Tính bằng cách thuận tiện:

    \(\dfrac{13}{19}\) + \(\dfrac{18}{19}\) + \(\dfrac{17}{19}\) 

=  \(\dfrac{13+18+17}{19}\)

= \(\dfrac{\left(13+17\right)+18}{19}\)

= \(\dfrac{48}{19}\)

\(\dfrac{12}{17}\) + \(\dfrac{19}{17}\) + \(\dfrac{8}{17}\)

= \(\dfrac{12+19+8}{17}\)

= \(\dfrac{\left(12+8\right)+19}{17}\)

= \(\dfrac{39}{17}\)

\(\frac{1}{2}\times\frac{1}{3}\times\frac{1}{4}=\frac{1\times1\times1}{2\times3\times4}=\frac{1}{24}\)

\(\frac{1}{2}\times\frac{1}{3}\div\frac{1}{4}=\frac{1}{2}\times\frac{1}{3}\times\frac{4}{1}=\frac{1\times1\times4}{2\times3\times1}=\frac{4}{6}=\frac{2}{3}\)

\(\frac{1}{2}\div\frac{1}{3}\times\frac{1}{4}=\frac{1}{2}\times\frac{3}{1}\times\frac{1}{4}=\frac{1\times3\times1}{2\times1\times4}=\frac{3}{8}\)

a, 2,3.4,5+2,3.2,5+7.7,7

= 2,3 (4,5+2,5)+7.7,7

= 2,3.7+7.7,7

= 7 (...)

bạn tự làm tiếp nha

c, 13,25:(0,5+0,25+0,125-0,25)

tự làm tiếp nha bạn

b, (0,1+0,2+0,2+0,4+0,5):3

tự làm tiếp nha bạn

a)2,3*4,5+2,3*2,5+7*7,7

=2,3*(4,5+2,5)+7*7,7

=2,3*7+7*7,7=7*(2,3+7,7)=7*10=70

b)0,1:3+0,2:3+0,3+0,4:3+0,5:3

=0,1:3+0,2:3+0,9:3+0,4:3+0,5:3

=(0,1+0,2+0,4+0,5+0,9)+:3

=2,1:3=0,7

Câu 1

A=21/4

B=3/16

C=41/8

D=1/2

Câu 2

Phải trồng tất cả:

280:70=4(cây)

Tick đi

 a )3/4+3/4:(2/3:2-1/6)

=3/2     :   1/3-1/6

=3/2     :     1/6

=9

b)  3/4-3/4:(2/3:2x4)

=   0        :1/3    x4

=  0           :     4/3

=    0

c ) 7-8/4+3/4:6

=5        +1/8

=41/8

d)4:5/4-3+3/10

=16/5  -33/10

=  - 1/10

2 giải              phải trồng cột là:

                        280:70=4( cột )

                             ĐS : 4 cột

tick nha

Bài 1:

 \(\dfrac{2}{3}\) + \(\dfrac{3}{4}\) - \(\dfrac{2}{5}\) 

=\(\dfrac{40}{60}\) + \(\dfrac{45}{60}\) - \(\dfrac{24}{60}\)

= \(\dfrac{61}{60}\)

b; \(\dfrac{12}{13}\) x \(\dfrac{3}{4}\)  - \(\dfrac{7}{13}\)

= \(\dfrac{9}{13}\) - \(\dfrac{7}{13}\)

= \(\dfrac{2}{13}\)

c; \(\dfrac{15}{17}\) : \(\dfrac{19}{34}\) - \(\dfrac{17}{19}\)

= \(\dfrac{15}{17}\) x \(\dfrac{34}{19}\) - \(\dfrac{17}{19}\)

= \(\dfrac{30}{19}\) - \(\dfrac{17}{19}\)

= \(\dfrac{13}{19}\)

Bài 2: 

a; \(\dfrac{x}{5}\) x \(\dfrac{3}{7}\) = \(\dfrac{9}{35}\)

     \(\dfrac{x}{5}\)       = \(\dfrac{9}{35}\) : \(\dfrac{3}{7}\)

      \(\dfrac{x}{5}\)      = \(\dfrac{3}{5}\)

       \(x\)      = \(\dfrac{3}{5}\) x 5

       \(x\)      = 3

Bài 1:

a)10234; 10236; 10238; 10246; 10248

b)10236; 10239; 12346; 12349; 13458

c) 12345; 10235; 10245; 12370; 14605

5/12 + 3/4 - 1/3 = 7/6 - 1/3 = 1/2

 1/4 - 3/7 + 11/14 = -5/28 + 11/14 = 17/28

a) \(\frac{5}{12}+\frac{3}{4}-\frac{1}{3}=\frac{5}{12}+\frac{9}{12}-\frac{4}{12}=\frac{5+9-4}{12}=\frac{10}{12}=\frac{5}{6}\)
b) \(\frac{1}{4}-\frac{3}{7}+\frac{11}{14}=\frac{7}{28}-\frac{12}{28}+\frac{22}{28}=\frac{7-12+22}{28}=\frac{17}{28}\)