81+9+91用乘法的运算定律计算
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81+9+91用乘法的运算定律计算
81+9+91用乘法的运算定律计算
81+9+91用乘法的运算定律计算
81+9+91=9X9+9+91
=(9X10)+90+1
=90+90+1
=90X2+1
=180+1
=181
81+9+91
=9X9+9+10X10-9
=9X10+10X10-9
=19X10-9
=190-9
=181
81+9+91
=9X9+9+10X10-9
=9X10+10X10-9
=19X10-9
=190-9
=181
解: 81+9+91=9X9+9+91 =(9X10)+90+1 =90+90+1 =90X2+1 =180+1 =181