首页
登录
职称英语
Machines X and Y run at different constant rates,and machine X can complete a ce
Machines X and Y run at different constant rates,and machine X can complete a ce
游客
2024-01-13
32
管理
问题
Machines X and Y run at different constant rates,and machine X can complete a certain job in 9 hours. Machine X worked on the job alone for the first 3 hours and the two machines,working together,then completed the job in 4 more hours.How many hours would it have taken machine Y, working alone,to complete the entire job?
选项
A、18
B、
C、
D、
E、
答案
A
解析
Machine X can complete the job in 9 hours, so it completed 1/3 of the job before machine Y started working. Since machine X worked 4 more hours, it completed 7/9 of the job, which left 2/9 of the job for machine Y to do during the 4 hours it worked together with machine X to complete the job. At this rate, machine Y would take (2/9) (4) = 18 hours to do the entire job working alone.
Alternatively, machine X can complete the job in 9 hours, so it completed — of the job before machine Y started working. This leaves 2/3 of the job, which took machines X and Y, working together, 4 hours to complete. So, if working together the machines took 4 hours to complete 2/3 of the job, it would take them 6 hours to do the whole job working together. Furthermore, rates are additive, so we should convert working times to rates. Machine X’s rate is — jobs per hour. Both machines together have a rate of 1/6 jobs per hour.
We must determine machine Y’s individual rate — for the whole job. First, add machine X’s rate to machine Y’s rate to get the combined rate. Then,
4/9+1/Y=1/6
1/Y=1/6-1/9
1/Y=2/36
Y=18
The correct answer is A.
转载请注明原文地址:https://tihaiku.com/zcyy/3360073.html
相关试题推荐
Whensheheardthebadnews,she______completely.A、brokeawayB、brokeupC、broke
W:Theexperimenthasbeencompleted,hasn’tit?M:______A、Yes.Weneedanothe
IftheDakotaAccessPipeline(输油管道)iscompleted,itwillcarrynearlyhalf
Thebuilding______willbecompletedinamonth.Itwillbeourlabbuilding.A、to
Historyisarecordofmankind;differenthistorians,______,interpretitdiff
Whensheheardthebadnews,she______completely.A、brokeawayB、brokeupC、bro
We’vetestedthreehundredtypesofboots,______iscompletelywaterproof.A、no
Withtheconstantchangeofconditions,theoutcomeisnotalways______.A、favora
Whensheheardthebadnews,she______completely.A、brokeawayB、brokeupC、brok
Acompletelynewsituationislikelyto______whentheschoolleavingageisrais
随机试题
【B1】[br]【B7】[originaltext]Anewbookissuretobediscussed,anddebated,
They______withtheworkinspiteoftheextremelydifficultconditions.A、carried
创新是一个民族进步的灵魂,是一个国家兴旺发达的不竭动力,也是一个政党永葆生机的源
某高层民用建筑采用加气混凝土砌块墙(双面抹灰粉刷)作为非承重的防火墙,下列(
对下面4个回络:110.125.129.0/24、110.125.1
老年患者比青年人使用洋地黄时更易出现毒副作用的原因是A.心输出量减少 B.神经
A.正负压通气 B.呼气末正压通气(PEEP) C.反比通气下列患者推荐机械
对于急性肾衰竭患者血容量状态的临床评估哪项提示血容量不足A.四肢水肿、肝淤血、肺
金融市场是资金融通市场,是指资金供应者和资金需求者双方通过信用工具进行交易而融通
关于政府直接隐性债务和或有债务的说法,正确的有()。A.直接债务是在任何情况下
最新回复
(
0
)