首页
登录
职称英语
[img]2022m10x/ct_ve01204002j_0002_221018[/img]In the figure above, X and Y repr
[img]2022m10x/ct_ve01204002j_0002_221018[/img]In the figure above, X and Y repr
游客
2024-01-13
42
管理
问题
In the figure above, X and Y represent locations in a district of a certain city where the streets form a rectangular grid. In traveling only north or east along the streets from X to Y, how many different paths are possible?
选项
A、720
B、512
C、336
D、256
E、56
答案
E
解析
Each possible path will consist of traveling a total of 3 grid segments north and 5 grid segments east. Thus, letting ’N’ represent traveling north by one grid segment and ’E’ represent traveling east by one grid segment, each path can be uniquely represented by an appropriate 8-character string of N’s and E’s. For example, as shown in the figure below, NEENEENE represents grid segments traveled in the order north, east, east, north, east, east, north, and east.
Therefore, the number of possible paths is equal to the number of appropriate 8-character strings of N’s and E’s, which is
.
since each appropriate string is determined when a specification is made for the 3 positions in the string at which the N’s are to be placed. Alternatively, the number of possible paths is equal to the number of permutations of 8 objects in which 3 are identical (the N’s) and the remaining 5 are identical (the E’s), and thus equal to
The correct answer is E.
转载请注明原文地址:http://tihaiku.com/zcyy/3360147.html
相关试题推荐
Itisnoteasy______theanswertothedifficultmathproblem.A、tofigureoutB
Itmakes______tofigureoutthesituationbeforetakinganyaction.A、senseB、mea
Itmakes______tofigureoutthesituationbeforetakinganyaction.A、senseB、mea
Itisnoteasy______theanswertothedifficultmathproblem.A、tofigureoutB、f
Inthefigureabove,whatisthevalueof2s-r?[img]2011q3/ct_egmatqj_egmatqchoo
Whichofthefollowingcouldbetheequationoflinelinthefigureabove?[img]
Inthefigureabove,x=2.WhatistheareaofcircleO?[img]2011q3/ct_egmatqj_eg
[img]2022m10x/ct_ve01204002j_0045_221018[/img]Thetableaboveshowsthecarren
Whatisthevalueofx?(1)x4+x2+1=[img]2022m10x/ct_ve01204002j_0044_22101
Ifd=[img]2022m10x/ct_ve01204002j_0015_221018[/img],a=c/2,andb=3c/4,whatist
随机试题
HavingbeenastudentandteacherinChina(atPekingandTsinghuaUniversit
[originaltext]Afteryearsofstudy,Ihavedeterminedthereareonlytwoty
ScientistsscanningandmappingtheGizapyramidssaythey’vediscoveredtha
Norrishasdecidedto_________forsomeeveningclassesnexttermnowthatheh
A.rootB.controlC.subjectsD.howeverE.realityF.sharpG.intense
根据我国宪法规定,国家监察委员会对全国人民代表大会和全国人民代表大会常务委员会负
A.甲胎蛋白阳性 B.癌胚抗原阳性 C.尿中Bence-Jones蛋白定性试
病态窦房结征合征病人最佳的治疗方法是A:静脉注射阿托品 B:口服麻黄碱 C:
关于索赔条款,下列说法正确的有()。A、异议与索赔条款一般是针对卖方交货质量、数
某日,社区民警小王入户走访时发现居民陆某因小儿子最近患重病住院手术,需高额手术费
最新回复
(
0
)