第32页作业题第1题答案
(1)(-1)+ 0 + 3
= (-1)+ 3
= 2
(2)(-10)+ 21 + (-13)
= [(-10)+(-13)] + 21
= (-23)+ 21
= -2
(3)3 +(-2.5)+(-4)
= 3 + [(-2.5)+(-4)]
= 3 +(-6.5)
= -3.5
第32页作业题第2题答案
(1)2.15 +(-4.25)+(-0.75)+(-230)
= 2.15 +(-4.25)+(-0.75)+(-0.15)
= [2.15 +(-0.15)] + [(-4.25)+(-0.75)]
= 2 +(-5)
= -3
(2)(-3/4)+(-1/6)+(+1/4)+(-5/6)
= [(-3/4)+(+1/4)] + [(-1/6)+(-5/6)]
=(-1/2)+(-1)
= -1又1/2.
理由略
第32页作业题第3题答案
解:(+120)+(-27.6)+(-5)+(-74)+(+16.8)+(-31.9)+(+25)
=(120 + 16.8 + 25)+[(-27.6)+(-5)+(-74)+(-31.9)]
= 161.8 +(-138.5)
= 23.3(元)
答:婷婷家这星期结余23.3元
第32页作业题第4题答案
解:(-2)+(+2)+(-3.5)+(-0.5)+(+3)+(+4)= 3(千克)
50 × 6 + 3 = 303(千克)
答:这6筐蔬菜的总质量为303千克
第32页作业题第5题答案
(1)(-3)+(-6)+(-2)=11
(2)(-2)+(+5)+(-3)=0
(注:答此题案不唯一)