Question

tính nhanh

19 x 64 + 76 x 34

35 x 12 + 65 x 13

136 x 68 + 16 x 272

( 2+4+6+...+ 100) x  ( 36 x 333-108 x 111)

19991999x 1998 - 19981998 x 1999

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Answer 1

19 x 64 + 76 x 34

= 19 x 64 + 19 x 4 x 34

= 19 x (64 + 4 x 34)

= 19 x 200

= 3 800

*****

35 x 12 + 65 x 13

= 35 x 12 + 65 x (12 + 1)

= 35 x 12 + 65 x 12 + 65

= 12 x (35 + 65) + 65

= 12 x 100 + 65

= 1 200 + 65

= 1 265

*****

136 x 68 + 16 x 272

= 136 x 68 + 16 x 4 x 68

= 68 x (136 + 16 x 4)

= 68 x (136 + 64)

= 68 x 200

= 13 600

*****

(2 + 4 + 6 + ... + 100) x (36 x 333 - 108 x 111)

= (2 + 4 + 6 + ... + 100) x (36 x 111 x 3 - 36 x 3 x 11)

= (2 + 4 + 6 + ... + 100) x 0

= 0 

*****

19991999 x 1998 - 19981998 x 1999

= 10 001 x 1999 x 1998 - 1998 x 10 001 x 1999

= 0