(1)1.25×16 (2)3.15+2.64+1.36+6.85 (3)14.28-1.5×0.3-3.55 (4)1-2+3-4+5-6+7-8…+2001-2002+2003-2004+2005.

问题描述:

(1)1.25×16
(2)3.15+2.64+1.36+6.85
(3)14.28-1.5×0.3-3.55
(4)1-2+3-4+5-6+7-8…+2001-2002+2003-2004+2005.

(1)1.25×16=1.25×8×2=10×2=20(2)3.15+2.64+1.36+6.85=(3.15+6.85)+(2.64+1.36)=10+4=14(3)14.28-1.5×0.3-3.55=14.28-0.45-3.55=14.28-(0.45+3.55)=14.28-4=10.28(4)1-2+3-4+5-6+7-8…+2001-2002+...