1. A) 225886 + 779 × 8

= 225886 + 6232

= 232118

B) 125 × 5 × 20 × 8

= (125 × 8) × (5 × 20)

= 1000 × 100

= 100000

C) 47286 : 2 + 14765

= 23643 + 14765

= 38408

D) 91428 - 23560 : 5

= 91428 - 4712

= 86716

3. A) 36 × 532 + 63 × 532 + 532

= 532 × (36 + 63 + 1)

= 532 × 100

= 53200

B) 679 × 123 + 679 - 679 × 24

= 679 × (123 + 1 - 24)

= 679 × 100

= 67900

C) 245 × 327 - 245 × 18 - 9 × 245

= 246 × (327 - 18 - 9)

= 245 × 300

= 73500

2. A) 6 × (x + 9845) = 29042

x + 9845 = 29042 : 6

x + 9845 = 14521/3

x = 14521/3 - 9845

x = -15014/3 < 0

Em xem lại đề vì lớp 4 chưa học số âm

B) (x : 3) × 8 = 8 × 3198

x : 3 = 3198

x = 3198 × 3

x = 9594

( 8/14 + 6/14 ) + ( 5/12 - 1/12 + 8/12 )

= 1 + ( 4/12 + 8/12 )

= 1 + 1 = 2

=(8/14+6/14 )+(5/12+8/12-1/12)

=1+1

=2

\(\frac{8}{14}+\frac{5}{12}+\frac{6}{14}+\frac{8}{12}-\frac{1}{12}\)

\(=\left(\frac{8}{14}+\frac{6}{14}\right)+\left(\frac{5}{12}+\frac{8}{12}-\frac{1}{12}\right)\)

\(=1+1\)

\(=2\)

\(\frac{8}{14}+\frac{5}{12}+\frac{6}{14}+\frac{8}{12}-\frac{1}{12}\)

\(=\)\(\left(\frac{8}{14}+\frac{6}{14}\right)+\left(\frac{5}{12}+\frac{8}{12}-\frac{1}{12}\right)\)

\(=\)\(1+1\)

\(=\)\(2\)

\(\frac{8}{14}\) \(+\) \(\frac{5}{12}\) \(+\) \(\frac{6}{14}\) \(+\) \(\frac{8}{12}\) \(-\) \(\frac{1}{12}\)

=   (  \(\frac{8}{14}\) \(+\) \(\frac{6}{14}\))    \(+\)(  \(\frac{5}{12}\) \(+\) \(\frac{8}{12}\) \(-\) \(\frac{1}{12}\))

=               \(1\)                    \(+\)                       \(1\)

=                           \(2\)

- Hok T - 

a) 47,54+18,72+5,13-17,54-7,72+4,87=(47,54-17,54)+(18,72-7,72)+(4,87+5,13)=30+11+10=51

b)4/7+7/13+17/9+19/13-8/9+17/7=(4/7+17/7)+(7/13+19/13)+(17/9-8/9)=3+2+1=6

3. Tính bằng cách thuận tiện nhất

A, 36 x 532 + 63 x 532 + 532

= (36 + 63 + 1) x 532 = 100 x 532 = 53 200

B, 679 x 123 + 679 - 679 x 24

= 679 x (123 + 1 - 24)

= 679 x 100 = 67 900

C, 245 x 327 - 245 x 18 - 9 x 245

= 245 x (327 - 18 - 9)

= 245 x 300

= 73 500

Bài 2:

a: \(6\cdot\left(x+9845\right)=29042\)

=>\(x+9845=\dfrac{29042}{6}=\dfrac{14521}{3}\)

=>\(x=\dfrac{14521}{3}-9845=-\dfrac{15014}{3}\)

b: \(\left(x:3\right)\cdot8=8\cdot3198\)

=>\(x:3=3198\)

=>\(x=3198\cdot3=9594\)

Bài 1:

a: \(225886+779\cdot8\)

\(=225886+6232\)

\(=232118\)

b: \(125\cdot5\cdot20\cdot8\)

\(=\left(125\cdot8\right)\cdot\left(5\cdot20\right)\)

\(=1000\cdot100=100000\)

c: \(47286:2+14765\)

\(=23643+14765\)

=38408

d: \(91428-23560:5\)

\(=91428-4712\)

=86716

`8,2 : 0,25 + 8,2 : 0,2 + 8,2`

`= 8,2 xx 4 + 8,2 xx 5 + 8,2 xx 1`

`= 8,2 xx (4 + 5 + 1)`

`= 8,2 xx 10`

`= 82`

`8,2 : 0,25 + 8,2 : 0,2 + 8,2`

`= 8,2 xx 4 + 8,2 xx 5 + 8,2`

`=8,2 xx (4+5+1)`

`=8,2 xx 10`

`= 82`

bằng 0 

2021 x 31 + 17 x 2021 + 47 x 2021 - 100 x 2021 + 5 x 2021 

= 2021 x ( 31 + 17 +47 + 5 - 100 )

=  2021 x 0 

=  0 .

         N H Ớ    T I C K    C H O    TUI   NHA    !

                   ~ HT~

= 0 nha

\(\dfrac{11}{34}+\dfrac{5}{23}+\dfrac{23}{34}+\dfrac{18}{23}\)
\(=\left(\dfrac{11}{34}+\dfrac{23}{34}\right)+\left(\dfrac{5}{23}+\dfrac{18}{23}\right)\)
\(=1+1\)
\(=2\)
#DatNe

=2

\(\dfrac{11}{34}+\dfrac{5}{23}+\dfrac{23}{34}+\dfrac{18}{23} =\left(\dfrac{11}{34}+\dfrac{23}{34}\right)+\left(\dfrac{5}{23}+\dfrac{18}{23}\right)=\dfrac{34}{34}+\dfrac{23}{23}=1+1=2\)

A=(1+10)+(2+9)+(3+8)+...+(5+6)

A=11.5=55

B=(1+19)+(3+17)+...+(9+11)

B=20.5=100

a=(1+9) + (2+8) + (3+7) + (4+6) + 5 + 10

=10 + 10 +10 +10 +10 + 5

=55