1.2+2.3+3.4+4.5+5.6+6.7+7.8/12+23+34+45+56+67+78_数学解答

1.2+2.3+3.4+4.5+5.6+6.7+7.8/12+23+34+45+56+67+78

人气：333 ℃　时间：2019-11-22 14:07:21

解答

1.2+2.3+3.4+4.5+5.6+6.7+7.8
=（1.2+7.8）×7÷2
=9×7÷2
=31.5
12+23+34+45+56+67+78
=（12+78）×7÷2
=90×7÷2
=315
=