a) 2070 + 414 x 4 x 28 - 138 x 3 x 17 = 41400

b) 2020 x 14 + 4040 x 16 + 6060 x 18 = 72720

c) 42 x 477 + 14 x 336 x 3 + 84 x 92 - 42 = 41832

a) 2070 + 414 x 4 x 28 - 138 x 3 x 17 = 41400

b) 2020 x 14 + 4040 x 16 + 6060 x 18 = 72720

c) 42 x 477 + 14 x 336 x 3 + 84 x 92 - 42 = 41832

2020 x 14 + 4040 x 16 + 6060 x 18

= 2020 x 14 + 2020 x 2 x 16 + 2020 x 3 x 18

= 2020 x 14 + 2020 x 32 + 2020 x 54

= 2020 x (14 + 32 + 54)

= 2020 x 100

= 202000

\(2020\times14+4040\times16+6060\times18\)

\(=2020\times14+2020\times2\times16+2020\times3\times18\)

\(=2020\times14+2020\times32+2020\times54\)

\(=2020\times\left(14+32+54\right)\)

\(=2020\times100\)

\(=202000\)

202000

Số số hạng là 19-11+1=9(số)

Tổng là: 10x9=90

=(11+19)+(12+18)+(13+17)+(14+16)+15

=30+30+30+30+15

=135

90

10-11+12-13+14-15+16-17+18-19+20
= (10+20)+(-11-19)+(12+18)+(-13-17)+(14+16)-15
= 30-30+30-30+30-15
= 15

(20 + 10) - (11 + 19) + ( 12 + 18 ) - ( 13 + 17 ) + ( 14 + 16 ) - 15

= 30 - 30 + 30 - 30 - 15

= -15

(20+10)-(11+19)+(12+18)-(13+17)+(14+16)-15

=30-30+30-30-15+30

=15

a.      19 + 18 + 17 + 16 + 14 + 21 + 22 +  23 + 24 + 26

= (19 + 21) + (18 + 22) + (17 + 23) + (16 + 24) + (14 + 26)

= 40 + 40 + 40 + 40 + 40

= 40 x 5

= 200

=2020

2020

=2020

a)     12 + 13 + 14 + 15 + 16 + 17+ 18

= (12 + 18) + ( 13 + 17) + (14 + 16) + 15

= 30 + 30 + 30 + 15

=  105

tính bằng cách thuận tiện nhất 6184+309+1516=

`9/14+19/18+19/14+35/18`

`=(9/14+19/14)+(19/18+35/18)`

`=28/14+54/18`

`=2+3`

`=5`

a) 52 x 2 + 48 x 2

   = (52 + 48) x 2

   =     100 x 2

   = 200

b) 10 + 12 + 14 + 16 + 18 + 20

   = (12 + 18) + (14 + 16) + (20 + 10)

   =       30     +     30      +      30

   =          90

100

90

200

90