[1+3+...+13+15] x[16 x2+4x16-32x3]                                                                                                                                                                =[1+3+...+13+15] x 0                                                                                                                                                                        =0

( 1 + 3 + .... + 13 + 15 ) x ( 16 * 2 + 4 * 16 - 32 * 3 )

= ( 1+ 3 + ... + 13 + 15) x ( 16 * 2 + 4 * 16 - 16 * 2 * 3)

= ( 1 + 3 + ...+ 13 + 15) x { [ 16 * ( 2 + 4 -  2 * 3 ) ] }

= ( 1 + 3 + ... + 13 + 15 ) x  16 * 0

= ( 1 + 3 + .... +13 +15 ) x 0

=0

`=432×(25+76)=432×101=43632`

\(=432\times\left(25+76\right)=432\times101=43632\)

\(432\cdot25+432\cdot76\\ =432.\left(25+76\right)\\ =432.101\\ =43632\)

=9/4x2/3+16/9x4/3

=18/12+64/36

=54/36+64/36=118/36=59/18

 36/16 x 12/18 + 32/18 x 24/18 

\(=\dfrac{9}{4}\times\dfrac{2}{3}+\dfrac{16}{9}\times\dfrac{4}{3}\)

\(=\dfrac{3}{2}+\dfrac{64}{27}\)

\(=\dfrac{209}{54}\)

a, =12 x ( 45 + 55 )

= 12 x 100 

= 1200

b, = 25 x 4 x 280

= 100 x 280

= 28000

c, = 268 x ( 192 -92)

= 268 x 100

= 26800

Câu 2: Tính bằng cách thuận tiện nhất:

\(a)\)\(12\times45+12\times55\)

\(=\)\(12\times\left(45+55\right)\)

\(=\)\(12\times100\)

\(=\)\(1200\)

\(b)\)\(25\times280\times4\)

\(=\)\(25\times4\times280\)

\(=\)\(100\times280\)

\(=\)\(28000\)

\(c)\)\(268\times192-92\times268\)

\(=\)\(268\times\left(192-92\right)\)

\(=\)\(268\times100\)

\(=\)\(26800\)

Trả lời :

a). 12 x 45 + 12 x 55 = 12 x ( 45 + 55 )

                                  = 12 x 100

                                  = 1200.

b). 25 x 280 x 4 =  280 x ( 25 x 4 )

                          = 280 x 100

                          = 28 000.

c). 268 x 192 - 92 x 268 = 268 x ( 192 - 92 )

                                       = 268 x 100

                                       = 26 800.

Nhớ k cho chị nha , Cảm ơn em.

16 x 98 + 16 x 2

= 16 x ( 98 + 2 )

= 16 x 100

= 1600

16 x 98 + 16 x 2

= 16 x ( 98 + 2 ) 

= 16 x 100 = 1600

= 16 x (98+2)

=16 x 100=1600

=16(8+2)=16*10=160

`16 xx 8 + 16 xx 2`

`=16 xx(8+2)`

`=16xx10`

`=160`

\(16\times8+16\times2\\ =16\times\left(8+2\right)\\ =16\times10\\ =160\)

64 x X + X + 32 x X + X x 3 = 805

(64+1+32+3) x X = 805

100 x X = 805

X = 805: 100

X = 8,05

2008 x 68 + 32 x 2008

= 2008 x (68 +32)

= 2008x100= 200800

64 x X + X + 32 x X + X x 3 = 805

X x ( 64 + 1 + 32 + 3 ) = 805

X x ( 65 + 35 ) = 805

X x 100 = 805

X = 805 : 100

X = 8,05

2008 x 68 + 32 x 2008

= 2008 x ( 68 + 32 )

= 2008 x 100

= 200800

b,21/17x13/14x56x3/42

=21/17x3/42x56x13/14

=21x3/17x42 x 56x13/14

=21x3/17x21x2 x 14x4x13/14

=3/17x2 x 4x13

=3/24 x 52=3x52/24

=3x52/3x8

=52/8=13/2

a, 6/7 x 16/15 x 7/6 x 21/32

=(6/7 x 7/6)x16/15x21/32

=16/15x21/32

=16x21/15x32

=16x3x7/3x5x16x2

=7/5x2=7/10

1/4

\(=\dfrac{8}{15}\left(\dfrac{25}{32}-\dfrac{10}{32}\right)=\dfrac{8}{15}\cdot\dfrac{15}{32}=\dfrac{1}{4}\)

( 25/32 - 10/32) x 8/15

 = 15/32 x 8/15

= 1/4