31.8×7'9+2.5×二又1/10-44.3×2.1要简算
31.8×7'9+2.5×二又1/10-44.3×2.1
=31.8*7.9+2.5*2.1-44.3*2.1
=31.8*7.9-2.1*（44.3-2.5）
=31.8*（7.9-2.1）
=31.8*5.8
=184.44
简便计算
31.8×7.9+19×1.25+44.3×2.1
=31.8×7.9+1.9×12.5+31.8×2.1+12.5×2.1
=31.8×（7.9+2.1）+（1.9+2.1）×12.5
=31.8×10+4×12.5
=318+50
=368
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