几条数学题,要简便,
⑴8.8×6+3.4×8
⑵1432×9090+1432×909
⑶51×49+3.51×49+51×3.51
⑷8.88×1.25×9+0.1
⑸15.37×7.89-9.37×7.89+15.37×2.11-9.37×2.11
⑹789×456456-456×789789
⑺[2+4+6+...+1998]-[1+3+5+...+1997]
⑻6+66+666+6666+66666
⑼99-97+95-93+91-89+...+11-9+7-5+3-1
⑽123÷25+3.6÷2.5+1.11÷0.25+1.05÷0.25