Hướng dẫn giải:

a) (426 + 813) : 3

Cách 1:

(426 + 813) : 3

= 1239 : 3

= 413

Cách 2:

(426 + 813) : 3

= 426 : 3 + 813 : 3

= 142 + 271 = 413

b) (2350 + 435) : 5

Cách 1:

(2350 + 435) : 5

= 2785 : 5

= 557

Cách 2:

(2350 + 435) : 5

= 2350 : 5 + 435 : 5

= 470 + 87 = 557

giúp mình nha

a: =60:4=15

Bài 1. Tính bằng hai cách

a) ( 19,8 + 3,9 ) ×2,5 =

Cách 1 : 23,7 x 2,5 = 59,25

Cách 2 : 19,8 x 2,5 + 3,9 x 2,5 = 49,5 + 9,75 = 59,25

b) (30,6 -14,9)×3,6 =

Cách 1 : 15,7 x 3,6 = 56,52

Cách 2 : 30,6 x 3,6 - 14,9 x 3,6 = 110,16 - 53,64 = 56,52

Phép tính : ( 426 + 813 ) : 3 

Cách 1 : ( 426 + 813 ) : 3 = 1239 : 3

                                         = 413

Cách 2 : ( 426 + 813 ) : 3 = 426 : 3 + 813 : 3

                                         = 142 + 271

và bằng 413 nhé

21 nha

a,C1 
 (5/6 + 5/8) x 2/3
= 35/24 x 2/3
=35/36
C2
 (5/6 + 5/8) x 2/3
= 5/6x2/3 + 5/8x2/3
= 10/18 + 10/24
= 35/36

b,C1
7/5 x 3/4 - 1/2 x 3/4
= 21/20 - 3/8
= 27/40
C2
7/5 x 3/4 - 1/2 x 3/4
=3/4 x (7/5-1/2)
=3/4x9/10
=27/40

a, 5/6 x (1/8x2/3) 

=5/6 x 1/12

=5/72

b,(7/5 - 1/2) x 3/4 

=0,9 x 3/4

=3,06

c,(5/6+5/8) x 2/3

=70/48 x 2/3

=35/36

a, 5/6 x (1/8x2/3) 

=5/6 x 1/12

=5/72

b,(7/5 - 1/2) x 3/4 

=0,9 x 3/4

=3,06

c,(5/6+5/8) x 2/3

=70/48 x 2/3

=35/36

`( 2/3 xx 4/5) xx 5/6`

`= 8/15 xx 5/6`

`= 40/90`

`=4/9`

__

`( 2/3 xx 4/5) xx 5/6`

`= 2/3 xx (4/5 xx 5/6)`

`= 2/3 xx 2/3`

`= 4/9`

-------

`(1/2 + 1/3) xx 1/5`

`= ( 3/6 +2/6) xx 1/5`

`= 5/6 xx1/5`

`= 5/30`

`=1/6`

__

`(1/2 + 1/3) xx 1/5`

`=1/2 xx 1/5 + 1/3 xx 1/5`

`= 1/10 + 1/15`

`=1/6`

a)

c1

`(2/3xx4/5)xx5/6`

`=8/15xx5/6`

`=4/9`

c2

`(2/3xx4/5)xx5/6`

`=2/3xx4/5xx5/6`

`=2/3xx5/6xx4/5`

`=5/9xx4/5`

`=4/9`

b)

c1

`(1/2+1/3)xx1/5`

`=(3/6+2/6)xx1/5`

`=5/6xx1/5`

`=1/6`

c2

`(1/2+1/3)xx1/5`

`=1/2xx1/5+1/3xx1/5`

`=1/10+1/15`

`=3/30+2/30`

`=5/30=1/6`

a) C1

 \(\dfrac{1}{8}\times\dfrac{5}{6}+\dfrac{5}{6}\times\dfrac{2}{3}=\dfrac{5}{6}\times\left(\dfrac{1}{8}+\dfrac{2}{3}\right)=\dfrac{5}{6}\times\dfrac{19}{24}=\dfrac{95}{144}\)

   C2

\(\dfrac{1}{8}\times\dfrac{5}{6}+\dfrac{5}{6}\times\dfrac{2}{3}=\dfrac{5}{48}+\dfrac{10}{18}=\dfrac{95}{144}\)

b) C1

  \(\dfrac{7}{5}\times\dfrac{3}{4}-\dfrac{1}{2}\times\dfrac{3}{4}=\dfrac{3}{4}\times\left(\dfrac{7}{5}-\dfrac{1}{2}\right)=\dfrac{3}{4}\times\dfrac{9}{10}=\dfrac{27}{40}\)

    C2 

   \(\dfrac{7}{5}\times\dfrac{3}{4}-\dfrac{1}{2}\times\dfrac{3}{4}=\dfrac{21}{20}-\dfrac{3}{8}=\dfrac{27}{40}\)

c) C1

 \(\left(\dfrac{5}{6}+\dfrac{5}{8}\right)\times\dfrac{2}{3}=\dfrac{35}{24}\times\dfrac{2}{3}=\dfrac{35}{36}\)

  C2 

  \(\left(\dfrac{5}{6}+\dfrac{5}{8}\right)\times\dfrac{2}{3}=\left(\dfrac{5}{6}\times\dfrac{2}{3}\right)+\left(\dfrac{5}{8}\times\dfrac{2}{3}\right)=\dfrac{5}{9}+\dfrac{5}{12}=\dfrac{35}{36}\)