两个简便运算,急~~1999+199.9+19.99+1.999+2.111 7.68-3.2+2.32-6.8

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两个简便运算,急~~
1999+199.9+19.99+1.999+2.111

7.68-3.2+2.32-6.8

1999+199.9+19.99+1.999+2.111
=(1999+1)+(199.9+1.1)+(19.99+0.01)+(1.999+0.001)
=2000+200+20+2
=2222
7.68 - 3.2 + 2.32 - 6.8
= (7.68+2.32)-(3.2+6.8)
=0