六年级数学简便运算(带答案) 十万火急!

用简便方法计算.
4 +3.2＋5 +6.8 25×(8×0.4)×1.25 7 又4/15-(2又4/15 -1/23)
=4+5+(3.2+6.8) =25×0.4×(8×1.25) =7 又4/15-2又4/15 +1/23
=9+10 =10× 10 =5+1/23
=19 =100 =5又1/23
(11/12+7/18+5/24 )×72 93.5÷3又1/2 ÷ 2/7 16÷2.5
=11/12×72+7/18×72+5/24×72 =93.5÷7/2× 7/2 =16÷5/2
=66+28+15 =93.5 =16×2/5
=109 =32/5
1125－997 998+1246+9989 （8700＋870＋87）÷87
=1125-1000+3 =1000-2+1246+10000-11 =8700÷87+870÷87+87÷87
=125+3 =11000+1246-13 =100+10+1
=128 =12233 =111
125×8.8 1.3+4.25+3.7+3.75 17.15-（3.5-2.85）
=125×8+125×0.8 =1.3+3.7+（4.25+3.75） =17.15+2.85-3.5
=1000+100 =5+8 =20-3.5
=1100 =13 =16.5