简算: ①57.5-14.25-153/4 ②102.31×59 ③(5/6×10.68+8.52×5/6)÷13/5 ④0.1+0.2+0.3+0.4+…+0.9+0.1+0.11+0.12+…+0
题目
答案
①57.5-14.25-15
=57.5-(14.25+15.75),
=57.5-30,
=27.5;
②102.31×59
=102.31×(60-1),
=102.31×60-102.31×1,
=6138.6-102.31,
=6036.29;
③(
×10.68+8.52×
)÷1
=[
×(10.68+8.52)]÷1
,
=
×19.2×
,
=10;
④0.1+0.2+0.3+0.4+…+0.9+0.1+0.11+0.12+…+0.98+0.99
=(0.1+0.9)×9÷2+(0.1+0.99)×90÷2,
=4.5+1.09×45,
=4.5+49.05,
=53.55.
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