7.用简便方法计算下面各题.
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7.用简便方法计算下面各题.
(1)66*21+19*21+85*19
(2)36*111+888*8
(3)99*99+199
要用简便方法计算,
(1)66*21+19*21+85*19
(2)36*111+888*8
(3)99*99+199
要用简便方法计算,
![7.用简便方法计算下面各题.](/uploads/image/z/15594245-53-5.jpg?t=7.%E7%94%A8%E7%AE%80%E4%BE%BF%E6%96%B9%E6%B3%95%E8%AE%A1%E7%AE%97%E4%B8%8B%E9%9D%A2%E5%90%84%E9%A2%98.)
(1)66*21+19*21+85*19
=21×(66+19)+85×19
=21×85+85×19
=85×(21+19)
=85×40
=3400
(2)36*111+888*8
=36×111+111×8×8
=36×111+64×111
=111×(36+64)
=111×100
=11100
(3)99*99+199
=99×(100-1)+199
=99×100-99+199
=9900+(199-99)
=9900+100
=10000
【学习宝典】团队为您答题.
=21×(66+19)+85×19
=21×85+85×19
=85×(21+19)
=85×40
=3400
(2)36*111+888*8
=36×111+111×8×8
=36×111+64×111
=111×(36+64)
=111×100
=11100
(3)99*99+199
=99×(100-1)+199
=99×100-99+199
=9900+(199-99)
=9900+100
=10000
【学习宝典】团队为您答题.