Question

用简便方法计算：19.88+9.9+198.8

Answer 1

观察该式，可将9.9写法10-0.1
198.8写成200-0.2，19.88写成20-0.12
再代入原式，所以原式
19.88+9.9+198.8
等于20-0.12+10-0.1+200-0.2
等于20+10+200-0.12-0.1-0.2
等于230-(0.12+0.1+0.2)
等于230-0.42
等于229.58

Answer 2

19.88+9.9+198.8
=19.88+19.88×10+9.9
=19.88×（1+10）+9.9
=19.88×11+9.9
=19.88×11+0.9×11
=11×（19.88+0.9）
=11×20.78
=（10+1）×20.78
=20.78×10+20.78
=207.8+20.78
=228.58