数学高手请进！

Question

①975x0.25+9又3/4x76-9.75

②333387又1/2x79+790x66661又1/4

③1-1/6+1/42+1/56+1/72

④(1+1/2+1/3+1/4)x(1/2+1/3+1/4+1/5)-(1+1/2+1/3+1/4+1/5)x(1/2+1/3+1/4)

⑤两辆汽车同时从东.西两站相向开出,第一次在离东站60千米的地方相遇,之后,两车继续以原来的速度前进.各自到达对方车站后都立即返回,又在距中点西侧30千米处相遇.两站相距多少千米?

⑥张师傅上班坐车,回家步行,路上一共要用80分钟.如果往返都坐车,全部行程要50分钟,如果往返都步行,全部行程要多长时间?

⑦一项工程,甲先单独做2天,然后与乙合作7天,这样才完成全工程的一半.已知甲乙工作效率的比是2:3.如果这件工作由乙单独做,需要多少天才能完成?

(需要过程!! 加分!!)

Answer 1

①975x0.25+9又3/4x76-9.75
=9.75*25+9.75*76-9.75
=9.75*(25+76-1)
=9.75*100
=975

②333387又1/2x79+790x66661又1/4
=333387又1/2x79+79x666612又1/2
=(333387又1/2+666612又1/2)*79
=1000000*79
=79000000

③1-1/6+1/42+1/56+1/72
=5/6+1/42+1/56+1/72
=35/42+1/42+1/56+1/72
=36/42+1/56+1/72
=6/7+1/56+1/72
=48/56+1/56+1/72
=49/56+1/72
=7/8+1/72
=63/72+1/72
=64/72

④(1+1/2+1/3+1/4)x(1/2+1/3+1/4+1/5)-(1+1/2+1/3+1/4+1/5)x(1/2+1/3+1/4)
=(1+1/2+1/3+1/4)x(1/2+1/3+1/4)+1/5*(1+1/2+1/3+1/4)-(1+1/2+1/3+1/4)*(1/2+1/3+1/4)- 1/5x(1/2+1/3+1/4)
=1/5*(1+1/2+1/3+1/4)-1/5x(1/2+1/3+1/4)
=1/5*1
=1/5

Answer 2

1、975x0.25+9又3/4x76-9.75
=9.75x1/4x100+9.75x76+9.75
=9.75x(1/4x100-1)+9.75x76
=9.75x24+9.75x76
=9.75x(24+76)
=9.75x100
=975
②333387又1/2x79+790x66661又1/4
=79x(333387又1/2+66661又1/4x10)
=79x(333387又1/2+66661又5/2)
=79x(333387又1/2+66663又1/2)
=79x400051
=
③1-1/6+1/42+1/56+1/72
=5/6+1/42+1/56+1/72
=35/42+1/42+1/56+1/72
=36/42+1/56+1/72
=6/7+1/56+1/72
=48/56+1/56+1/72
=49/56+1/72
=7/8+1/72
=63/72+1/72
=64/72
剩下的改天回答你。