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问题: 小学数学题简便

( 1 ) 394+359+369+379+389+399+400

解答:

394+359+369+379+389+399+400
=390+360+370+380+390+(400-1)+400
=300+400+400+400+(400-10)+(400-1)+400
=400*7-100-10-1
=2800-111
=2689