9的乘法口诀
按规律填一填。
9×1=9 ······( )个9相加,比10少1;
9×2=18 ······( )个9相加,比20少2;
9×3=( )······( )个9相加,比( )少( );
9×4=( )······( )个9相加,比( )少( );
9×5=( )······( )个9相加,比( )少( );
9×6=( )······( )个9相加,比( )少( );
9×7=( )······( )个9相加,比( )少( );
9×8=( )······( )个9相加,比( )少( );
9×9=( )······( )..