\(A=\dfrac{404\times25+75\times404}{2038-9-9}\)

\(=\dfrac{404\times\left(25+75\right)}{2029-9}\)

\(=\dfrac{404\times100}{2020}\)

\(=\dfrac{40400}{2020}\)

\(=20\)

#\(Toru\)

(25x36):9+450-75-25

= 900 : 9 + 450 - 75 -25

= 100 + ( 450 - 75-25)

= 100 + 350

= 450

450

=450

= 25 x 75/100 + 75 x 0.92 + 25 x 0.25 + 75 x 8/100
= 25 x 0.75 + 75 x 0.92 + 25 x 0.25 + 75 x 0.08
= 25 x ( 0.75 + 0.25 ) + 75 x ( 0.92 + 0.08 )
= 25 x 1 + 75 x 1 
= ( 25 + 75 ) x 1 
= 100 x 1
= 100

… = 25 x (36 : 9) = 25 x 4 = 100

(25 x 36) : 9 = 25 x (36 : 9) = 25 x 4 = 100

phòng có số bộn bàn ghế là : 240 : 15 = 16 [bộ]                                                                                                                                                                                             đ/s:16 bộ

a) \(6,25+8,75+3,75+1,25=6,25+3,75+8,75+1,25=10+10=20\)

b) \(7,15:0,5+7,15x9-7,15=7,15x\left(1:0,5+7,19-1\right)=7,15x\left(2+9-1\right)=7,15x10=71,5\)

`@` `\text {Ans}`

`\downarrow`

`a)`

`6,25 + 8,75 + 3,75 + 1,25 `

`= (6,25 + 3,75) + (8,75 + 1,25)`

`= 10 +10 = 20`

`b)`

` 7,15 \div 0,5 + 7,15 \times 9 - 7,15 `

`= 7,15 \times 2 + 7,15 \times 9 - 7,15 \times 1`

`= 7,15 \times ( 2+ 9 - 1)`

`= 7,15 \times 10`

`= 71,5`

a, 2x9x5x7x4x25

=2x5x4x25x9x7

=10x100x63

=63000

b,6x14x5x25x3x4

=6x5x3x4x25x14

=90x100x14

=9000x14

=126000

~HT~

\(2\times9\times5\times7\times4\times\)\(25\)

\(=\left(2\times5\right)\times\left(25\times4\right)\)\(\times\left(9\times7\right)\)

\(=10\times1000\times63\)

\(=630000\)