练习六
1、60+255+40
=60+40+255
=100+255
=355
282+41+159
=282+(41+159)
=282+200
=482
548+52+468
=600+468
=1068
=500
800-138-162
=800- (138+162)
=800-300
=500
672-36-64
=672- (36+64)
=672 -100
=572
672-36+64
=636+64
=700
13+46+55+54+87
= (13+87)+(46+54)+55
=100+100+55
=255
5+137+45+63+50
= (5-1-45)+(137+63)+50
=50+200+50
= (50+50)+200
=300
2、 225+328+175=728(元)
3、2000 - 416 - 284
=2000-(416+284)
=1300(米)
4、1+2+3+4+5+6+7+8+9+ 10 =(1+10) ×10÷2=55(根)
5、(从上到下)107 104 106 38
6、25 提示:325-276-24=25(票)
7、2255+355+245=2855(元)
8、(104-4)+(78-8) =170(名)
9、(1)1+2+3+4+---+98+99+100
=(1+100) X100÷2
=5050
(2)2+4+6+-+16+18+20
= (2+20) X10÷2
=110
(3)20-19+18+17+ ... +4 - 3+2-1
= (20-19) +(18-17)+…+1+(4-3)-(2-1)
=1+1+…+1+1
=1×10=10
