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
31
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
Theprivatecarisassumedtohavewidenedourhorizonsandincreasedourm
Widespreadadoptionofplug-inelectricvehiclescoulddramaticallycutgree
【B1】[br]【B8】[originaltext]Italiansareknownforthemandtheoriessuggestt
训练中运动负荷越大越好。()
下列各项中,不属于公路监控设施应当具备的功能的是()。A.信息采集 B.
回答有关贝克曼梁法测试弯沉的测试步骤的问题。(2)贝克曼梁的后臂与前臂之比为(
A.玻璃样变性 B.细胞水肿 C.纤维素样变性坏死 D.脂肪变性肝细胞内圆
“阿基米德将被永远铭记,而剧作家埃斯库罗斯将会被遗忘,因为语言会消亡而数学理念
王某于1999年在某城市中心城区购买了一幢6层的百货大厦,为保证正常经营,于20
目前,收取承销费用的标准是()。 A.包销商收取的包销佣金为包销股票总金额的
最新回复
(
0
)