Question

①99999×7778+33333×66666②3.6×25.4+37.9×6.4③ 1 1 2 - 5 6 + 7 12

①99999×7778+33333×66666②3.6×25.4+37.9×6.4③ 1 1 2 - 5 6 + 7 12 - 9 20 + 9 30 - 13 42 ④ 5 4 ×17.6+36÷ 4 5 +2.64×12.5．

Answer 1

①99999×7778+33333×66666 =99999×7778+33333×3×22222， =99999×77778+99999×22222， =99999×（77778+22222）， =99999×100000， =9999900000； ②3.6×25.4+37.9×6.4 =3.6×25.4+（25.4+12.5）×6.4， =3.6×25.4+25.4×6.4+12.5×6.4， =3.6×25.4+25.4×6.4+12.5×8×0.8 =25.4×（3.6+6.4）+100×0.8， =254+80， =334； ③ 1 1 2 - 5 6 + 7 12 - 9 20 + 9 30 - 13 42 = 3 1 - 3 2 + 5 2 - 5 3 + 7 3 - 7 4 + 9 4 - 9 5 + 9 5 - 9 6 + 13 6 - 13 7 ， =3+（ 5 2 - 3 2 ）+（ 7 3 - 5 3 ）+（ 9 4 - 7 4 ）+（ 9 5 - 9 5 ）+（ 13 6 - 9 6 ）- 13 7 ， =3+1+ 2 3 + 1 2 +0+ 2 3 - 13 7 ， =3 41 42 ； ④ 5 4 ×17.6+36÷ 4 5 +2.64×12.5 =1.25×17.6+36×1.25+26.4×1.25， =（17.6+26.4+36）×1.25， =80×1.25， =100．