【答案解析】
1.71-13-22觀察算式發(fā)現(xiàn)減數(shù)13、22分別是比整10和整20大的數(shù)。可以把-13拆成-10-3,把-22拆成-20-2如下:
71-13-22
=71-10-3-20-2
=71-10-20-3-2
=43-5
=33+10-5
=33+5
=38
2.53-19-18
=53-20+1-20+2
=50-20-20+1+2
=10+3
=13
3.62-39-13
=62-40+1-10-3
=62-40-10+1-3
=12+1-3
=10