5,10,15,20,25,30,35,40,45,50

bảng nhân 5 

5 x 1 =5

5 x 2 =10

5 x 3 =15

5 x 4 =20

5 x 5 =25

5 x 6 =30

5 x 7 =35

5 x 8 =40

5 x 9 =45

5 x 10 =50

= 25 * 5 + 15 * 5 + 60 * 5 *1 ( tớ viết dấu sao thay dấu nhân ) 

=5*(25+ 15 + 60+ 1)

=5* 100

=500

428 x 12 - 428 x 2

= 428 x (12 - 2)

= 4280

Chỉ biết 2 câu đầu hoi

Chúc em học tốt tick cho chị nha

995 x 5 + 4 x 5 + 5

= 995 x 5 + 4 x 5 + 5 x 1

= ( 995 + 4 + 1 ) x 5

= 1000 x 5

= 5000

655 x 6 - 355 x 6

= ( 655 - 355 ) x 6

= 300 x 6

= 1800

25 x 5 + 15 x 5 + 60 x 5

= ( 25 + 15 + 60 ) x 5

= 100 x 5

= 500

428 x 97 + 428 x 2 + 428

= 428 x 97 + 428 x 2 + 428 x 1

= 428 x ( 97 + 2 + 1 )

= 428 x 100

= 42800

Hướng dẫn giải:

a) 3 x (20 – 5)

Cách 1:

3 x (20 – 5) = 3 x 15 = 45

Cách 2:

3 x (20 – 5) = 3 x 20 – 3 x 5 = 60 – 15 = 45

b) 20 x (40 – 1)

Cách 1:

20 x (40 – 1) = 20 x 39 = 780

Cách 2:

20 x (40 – 1) = 20 x 40 – 20 x 1 = 800 – 20 = 780

5 x 6 x 5 x 2 x 5 x 4 x 5 x 3

=(5x6) x (5x2) x (5x4) x (5x3)

=30 x 10 x20 x15

=(30x10)x(20x15)

=300x300

=90000

( 5 x 5 x 5 x 5 ) x ( 6 x 2 x 4 x 3 ) 

= 625 x 144

= 90 000 

tick dùm ~~

=240 000 

tick cái bạn tòn 280

4 x 5 x 6 x 8 x 5 x 2 x 5 x 5 

=(4 x 5 x 5) x (8 x 5 x 5) x 6 x 2

=100 x 200 x 12

=20000 x 12

=240 000

5 x 6 x 8 x 5 x 4 x 5 x 2 x 5=240.000

a. 3/5 x 5 + 12 x 3/5 + 3 : 5/3

= 3/5 x 5 + 12 x 3/5 + 3 x 3/5

= 3/5 x ( 5 + 15 + 3)

= 3/5 x 20

= 12

b. 3/5 x 45/27 x 135/180

= 3/5 x 5/3 x 3/4

= 1 x 3/4

= 3/4

a,3/5.(5+12+1/3)

=3/5.52/3

=52/5

b,=3/5.5/3.3/4

=1.3/4

=3/4

a, \(\left(\frac{4}{9}.\frac{3}{7}\right).\frac{7}{4}=\frac{4}{9}\left(\frac{3}{7}.\frac{7}{4}\right)=\frac{4}{9}.\frac{3}{4}=\frac{3}{9}=\frac{1}{3}\)

b, \(\left(\frac{6}{5}.\frac{4}{5}\right).\frac{25}{16}=\frac{6}{5}\left(\frac{4}{5}.\frac{25}{16}\right)=\frac{6}{5}.\frac{5}{4}=\frac{6}{4}=\frac{3}{2}\)

c, \(\left(\frac{7}{8}.\frac{16}{9}\right).\frac{3}{14}=\frac{7}{8}\left(\frac{16}{9}.\frac{3}{14}\right)=\frac{7}{8}.\frac{8}{21}=\frac{7}{21}=\frac{1}{3}\)

a, $\left(\frac{4}{9}.\frac{3}{7}\right).\frac{7}{4}=\frac{4}{9}\left(\frac{3}{7}.\frac{7}{4}\right)=\frac{4}{9}.\frac{3}{4}=\frac{3}{9}=\frac{1}{3}$

b, $\left(\frac{6}{5}.\frac{4}{5}\right).\frac{25}{16}=\frac{6}{5}\left(\frac{4}{5}.\frac{25}{16}\right)=\frac{6}{5}.\frac{5}{4}=\frac{6}{4}=\frac{3}{2}$

c, $\left(\frac{7}{8}.\frac{16}{9}\right).\frac{3}{14}=\frac{7}{8}\left(\frac{16}{9}.\frac{3}{14}\right)=\frac{7}{8}.\frac{8}{21}=\frac{7}{21}=\frac{1}{3}$