怎样简便就怎样算①0.25×1.25×0.8×0.4②[(25%-112)×316]÷0.375③1990×198.9-1989×198.8④2007÷200720072008+12009⑤(1+19105)+(1+19105×2)+(1+19105×3)+…(1+19105×20)-数学
题文
怎样简便就怎样算 ①0.25×1.25×0.8×0.4 ②[(25%-
③1990×198.9-1989×198.8 ④2007÷2007
⑤(1+
|
答案
①0.25×1.25×0.8×0.4, =(0.25×0.4)×(1.25×0.8), =0.1×1, =0.1; ②[(25%-
=[
=
=
③1990×198.9-1989×198.8, =1990×198.9-198.9×1988, =×198.9, =2×198.9, =397.8; ④2007÷2007
=2007÷
=2007÷
=2007÷
=2007×
=
=1; ⑤(1+
|