Đáp số: 1200

Câu A là :2x19x6+3x37x4+44x12=228+444+528=1200

Câu B là:18x15+35+15x32+35x49=270+35+480+1715=(1715+35)+(270+480)=1750+750=1500

2.19.6 + 3.37.4 + 44.12

= 12 .19 + 12.37 + 44.12

= 12.(19+37+44)

= 12.100 = 1200

18.15 + 35 + 15.32 + 35.49

= 15.(18+32) + 35.(1+49)

= 15. 50 + 35.50

= 50.(15+35)

= 50.50

= 2500

2.9.6+3.37.4+44.12

=2.6.9+3.4.37+44.12

=12.9+12.37+44.12

=12. (9+37+44)

=12.90

=1080

2.9.6+3.37.4+44.12

=2.3.3.3.2+3.37.4+44.4.3

=4.3.3.3+3.4.37+44.3.4

=3.4.(3.3+37+44)

=12.80

=960

=600+5+300+25+4=934''

=600+5+320+9=920+14=934

lên lớp 6 rồi, câu này tính ra lun đi, sao cô còn bảo tính nhanh làm j nhỉ  ( ? . ? )

605 + 329 

= 600 + 5 + 300 + 29

= ( 600 + 300 ) + ( 5 + 29 )

= 900 + 34

=934

Học tốt

&YOUUBER&

\(A=\dfrac{5}{4x7}+\dfrac{5}{7x10}+...+\dfrac{5}{25x28}+\dfrac{5}{28x31}\)

\(\dfrac{3}{5}A=\dfrac{7-4}{4x7}+\dfrac{10-7}{7x10}+...+\dfrac{28-25}{25x28}+\dfrac{31-28}{28x31}\)

\(\dfrac{3}{5}A=\dfrac{7}{4x7}-\dfrac{4}{4x7}+\dfrac{10}{7x10}-\dfrac{7}{7x10}+...+\dfrac{28}{25x28}-\dfrac{25}{25x28}+\dfrac{31}{28x31}-\dfrac{28}{28x31}\)

\(\dfrac{3}{5}A=\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+...+\dfrac{1}{25}-\dfrac{1}{28}+\dfrac{1}{28}-\dfrac{1}{31}\)

\(\dfrac{3}{5}A=\dfrac{1}{4}-\dfrac{1}{31}=\dfrac{27}{124}\)

\(A=\dfrac{27}{124}:\dfrac{3}{5}=\dfrac{27}{124}x\dfrac{5}{3}=\dfrac{45}{124}\)

=600

=600

600 nhé

A = \(\dfrac{1\times2\times3\times4\times5\times6\times....\times100\times101}{3\times4\times5\times6\times.......\times100}\)

A = 1 x 2 x 101 x \(\dfrac{3\times4\times5\times6\times........\times100}{3\times4\times5\times6.............\times100}\)

A =   1 x 2 x 101 x 1 

A = 202

\(\dfrac{1.2.3.4.5....101}{3.4.5.6.100}\)

Ta thấy phần tử sẽ triệt tiêu hết cho mẫu nên mẫu sẽ bằng 1 

=> \(\dfrac{2.101}{2}=202\)

\(15.14.12.25.2=15.14.\left(4.3\right).25.2\)

     \(=15.2.25.4.14.3=30.100.42\)

               \(=3000.42=126000\)

#Hok_tốt

\(15\cdot14\cdot12\cdot25\cdot2\)

\(=3\cdot5\cdot2\cdot7\cdot3\cdot4\cdot25\cdot2\)

\(=\left(3\cdot3\right)\cdot\left(5\cdot2\right)\cdot\left(4\cdot25\right)\cdot2\cdot7\)

\(=9\cdot10\cdot100\cdot2\cdot7\)

\(=9000\cdot2\cdot7\)

\(=18000\cdot7\)

\(=126000\)

\(15\cdot14\cdot12\cdot25\cdot2\)

\(=15\cdot14\cdot3\cdot4\cdot25\cdot2\)

\(=1260\cdot100\)

\(=126000\)