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19.81×0.1+0.5×198.1+0.049×1981这道题想怎样简便不用计算只用口算,

题目详情
19.81×0.1+0.5×198.1+0.049×1981这道题想怎样简便不用计算只用口算,
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答案和解析
19.81×0.1+0.5×198.1+0.049×1981=19.81×0.1+19.81×5+19.81×4.9=19.81(0.1+4.9)+19.81×5=19.81×5+19.81×5=19.81×10=198.1