21.8*2.9+3.99[简算]要求用简算,要有简算步骤,简算步骤要写完整.
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![21.8*2.9+3.99[简算]要求用简算,要有简算步骤,简算步骤要写完整.](/uploads/image/z/16128-0-8.jpg?t=21.8%2A2.9%2B3.99%5B%E7%AE%80%E7%AE%97%5D%E8%A6%81%E6%B1%82%E7%94%A8%E7%AE%80%E7%AE%97%2C%E8%A6%81%E6%9C%89%E7%AE%80%E7%AE%97%E6%AD%A5%E9%AA%A4%2C%E7%AE%80%E7%AE%97%E6%AD%A5%E9%AA%A4%E8%A6%81%E5%86%99%E5%AE%8C%E6%95%B4.)
21.8*2.9+3.99[简算]要求用简算,要有简算步骤,简算步骤要写完整.
21.8*2.9+3.99[简算]
要求用简算,要有简算步骤,简算步骤要写完整.
21.8*2.9+3.99[简算]要求用简算,要有简算步骤,简算步骤要写完整.
21.8*2.9+3.99
=21.8*(3-0.1)+(4-0.01)
=21.8*3-21.8*0.1+4-0.01
=65.4-2.18+4-0.01
=(65.4+4)-(2.18+0.01)
=69.4-2.19
=67.21