( 1996 + 7984 ) + ( 3992 + 5988 ) = 9980 + 9980 = 19960
1996+3992+5988+7984
=1x1996+2x1996+3x1996+4x1996
=(1+2+3+4)x1996
=10x1996
=19960
k minh với
1996 + 3992 + 5988 + 7984
= ( 1996 + 7984 ) + ( 3992 + 5998 )
= 9980 + 9980
= 9980 x 2
= 19960
1996+3992+5988+7984
= ( 1996+7988) + ( 3992+ 5988)
= 9980 + 9980
= 19960
1996 + 3992 + 5988 + 7984
=(1996 + 7984)+(3992 + 5988)
=9980 + 9980
=19960