怎样简便怎样算66*21+19*21+85*19
问题描述：
怎样简便怎样算66*21+19*21+85*19
答
66*21+19*21+85*19
=85*21+85*19
=85*40=3400
答
=3 400
可能是类似（p+1）（q+1）=pq+p+q+1
答
66*21+19*21+85*19
=21x(66+19)+85*19
=21x85+85x19
=85x(21+19)
=85x40
=3400