999.9+99.9+9.9+0.9
=1000-0.1+100-0.1+10-0.1+1-0.1
=1111-0.4
=1110.6
497-97*3+37
=497-100*3+3*3+37
=497+3-300+3+3+37
=243
简便计算 999.9+99.9+9.9+0.9和497-97×3+37
999.9+99.9+9.9+0.9
=1000-0.1+100-0.1+10-0.1+1-0.1
=1111-0.4
=1110.6
497-97*3+37
=497-100*3+3*3+37
=497+3-300+3+3+37
=243