用你喜欢的方法计算. 9+99+999+9999+99999 124.68+324.68+524.68+724.68+924.68 998×999999-999×998998 17.48×37-174.8×1.9+17.48×82.
问题描述:
用你喜欢的方法计算.
9+99+999+9999+99999
124.68+324.68+524.68+724.68+924.68
998×999999-999×998998
17.48×37-174.8×1.9+17.48×82.
答
(1)9+99+999+9999+99999,
=(10-1)+(100-1)+(1000-1)+(10000-1)+(100000-1),
=111110-5,
=111105;
(2)124.68+324.68+524.68+724.68+924.68,
=(100+24+0.68)+(300+24+0.68)+(500+24+0.68)+(700+24+0.68)+(900+24+0.68),
=(100+300+500+700+900)+24×5+0.68×5,
=2500+120+3.4,
=2623.4;
(3)998×999999-999×998998,
=998×999×1001-999×998×1001,
=0;
(4)17.48×37-174.8×1.9+17.48×82,
=17.48×37-17.48×19+17.48×82,
=17.48×(37-19+82),
=17.48×100,
=1748.