教你如何作笔试题math centre Numeracy大型外企业笔试必备.docx
- 文档编号:5729305
- 上传时间:2022-12-31
- 格式:DOCX
- 页数:24
- 大小:193.09KB
教你如何作笔试题math centre Numeracy大型外企业笔试必备.docx
《教你如何作笔试题math centre Numeracy大型外企业笔试必备.docx》由会员分享,可在线阅读,更多相关《教你如何作笔试题math centre Numeracy大型外企业笔试必备.docx(24页珍藏版)》请在冰豆网上搜索。
教你如何作笔试题mathcentreNumeracy大型外企业笔试必备
ANumeracyRefresher
V2.January2005
ThismaterialwasdevelopedandtrialledbystaffoftheUniversityofBirminghamCareersCentreandsubsequentlyusedwidelythroughouttheHESector.ThecontributionsofTomFrank,EricWilliamsandClareWrightareparticularlyacknowledged.
www.mathcentre.ac.uk
©2004mathcentre
IMPROVE
YOUR
NUMERACY
UniversityofBristol
CareersAdvisoryService
INTRODUCTION
Manystudentsworryaboutanythingtodowithnumbers,havingdonelittlesincetheirGCSEs.Thisbooklethasbeendesignedtoofferpracticeandexplanationinbasicprocesses,particularlytoanyonefacingemployers’selectiontests.ItusesmaterialdevelopedbyClareWright,TomFrank,andEricWilliamsofBirminghamUniversityCareersCentre,whereithasbeensuccessfullyusedforsometime.
Regainingnumericalconfidencecantakealittlewhilebut,ifyouoncehadthebasicskills,practiceshouldbringthemback.If,however,youencounterrealproblemsperhapsyoushouldquestionyourmotives.Employersdon’ttestyoujusttomakelifedifficult.Theydoitbecausetheirjobsdemandaparticularlevelofproficiency.Ifyou’restrugglingtomeetthatlevel,ornotenjoyingit,istheirjobrightforyou?
CONTENTS
1.
Decimals……………………………………………………………………………………………….
page
2
2.
Fractions………………………………………………………………………………………………
5
3.
Approximations……………………………………………………………………………………
10
4.
Averages……………………………………………………………………………………………….
12
5.
Percentages………………………………………………………………………………………….
14
6.
Ratios…………………………………………………………………………………………………….
17
7.
Answers…………………………………………………………………………………………………
19
SECTION1-DECIMALS
Themostcommonuseofdecimalsisprobablyinthecostofitems.Ifyou’veworkedinashoporpub,you’reprobablyalreadyfamiliarwithworkingwithdecimals.
AdditionandSubtraction
Thekeypointwithadditionandsubtractionistolineupthedecimalpoints!
Example1
2.67+11.2=2.67
+11.20inthiscase,ithelpstowrite11.2as11.20
13.87
Example2
14.73–12.157=14.730againaddingthis0helps
-12.157
2.573
Example3
127.5+0.127=127.500
+0.127
127.627
Multiplication
Whenmultiplyingdecimals,dothesumasifthedecimalpointswerenotthere,andthencalculatehowmanynumbersweretotherightofthedecimalpointinboththeoriginalnumbers-next,placethedecimalpointinyouranswersothattherearethisnumberofdigitstotherightofyourdecimalpoint.
Example4
2.1x1.2.
Calculate21x12=252.Thereisonenumbertotherightofthedecimalineachoftheoriginalnumbers,makingatotaloftwo.Wethereforeplaceourdecimalsothattherearetwodigitstotherightofthedecimalpointinouranswer.
Hence2.1x1.2=2.52.
Alwayslookatyouranswertoseeifitissensible.2x1=2,soouranswershouldbecloseto2ratherthan20or0.2whichcouldbetheanswersobtainedbyputtingthedecimalinthewrongplace.
Example5
1.4x6
Calculate14x6=84.Thereisonedigittotherightofthedecimalinouroriginalnumberssoouransweris8.4
Check1x6=6soouranswershouldbecloserto6than60or0.6
Division
Whendividingdecimals,thefirststepistowriteyournumbersasafraction.Notethatthesymbol/isusedtodenotedivisioninthesenotes.
Hence2.14/1.2=2.14
1.2
Next,movethedecimalpointtotherightuntilbothnumbersarenolongerdecimals.Dothisthesamenumberofplacesonthetopandbottom,puttinginzerosasrequired.
Hence2.14becomes214
1.2120
Thiscanthenbecalculatedasanormaldivision.
Alwayscheckyouranswerfromtheoriginaltomakesurethatthingshaven’tgonewrongalongtheway.Youwouldexpect2.14/1.2tobesomewherebetween1and2.Infact,theansweris1.78.
Ifthismethodseemsstrange,tryusingacalculatortocalculate2.14/1.2,21.4/12,214/120and2140/1200.Theanswershouldalwaysbethesame.
Example6
4.36/0.14=4.36=436=31.14
1.1414
Example7
27.93/1.2=27.93=2793=23.28
1.2120
RoundingUp
Somedecimalnumbersgoonforever!
Tosimplifytheiruse,wedecideonacutoffpointand“round”themupordown.
Ifwewanttoround2.734216totwodecimalplaces,welookatthenumberinthethirdplaceafterthedecimal,inthiscase,4.Ifthenumberis0,1,2,3or4,weleavethelastfigurebeforethecutoffasitis.Ifthenumberis5,6,7,8or9we“roundup”thelastfigurebeforethecutoffbyone.2.734216thereforebecomes2.73whenroundedto2decimalplaces.
Ifweareroundingto2decimalplaces,weleave2numberstotherightofthedecimal.
Ifweareroundingto2significantfigures,weleavetwonumbers,whethertheyaredecimalsornot.
Example8
243.7684=243.77(2decimalplaces)
=240(2significantfigures)
1973.285=1973.29(2decimalplaces)
=2000(2significantfigures)
2.4689=2.47(2decimalplaces)
=2.5(2significantfigures)
0.99879=1.00(2decimalplaces)
=1.0(2significantfigures)
Trytheseexamples.Giveallyouranswersto2decimalplacesand2significantfigures
1.2.45+7.682.3.17+12.153.2.421+13.1
4.162.5+2.1735.12.5–3.76.9.6–7.8
7.163.5–2.1738.2.416–1.49.26.95–1.273
10.1.5x7.211.2.73x8.1412.6.25x17x3
13.2.96x17.314.4.2/1.715.53.9/2.76
16.14.2/6.117.2.5/0.0318.250/2.35
Answersonpage19
SECTION2-FRACTIONS
CancellingDown
Whenweuseafraction,weusuallygiveitinitssimplestform.Todothiswelookatthetop(thenumerator)andthebottom(denominator)andseeifthereisanumberbywhichbothcanbedividedanexactnumberoftimes.
Hence2=1x2=1sincethetwos“cancelout”
84x24
E.G.6=3x2=3
84x24
15=3x5=3
357x57
16=8x2=2OR16=4x4=4=2x2=2
248x33246x463x23
Useasmanystepsasyouneedtoreachtheanswer.
AddingFractions
Whenthedenominators(thebottomlines)areallthesame,yousimplyaddthetopline(numerators)
Eg:
2+3=2+3=55+3=5+3=8
66669999
Remembertocanceldownifnecessary.
Whenthedenominatorsaredifferent,weneedtochangethefractionssothatthedenominatorsarethesamethenwecanaddthetoplineasabove.
Supposewewishtocalculate1+1
24
Fromthecancellingdownprocess,weknowthat1=1x2=2
22x24
Thedenominatorsofbothfractionsarenowthesamesowecancalculate
1+1=2+1=2+1=3
244444
Sometimesthedenominatorsarenotmultiplesofeachother
Eg:
1+2
43
Inthiscasewecanmake12thecommondenominatorusing
1=1x3=32=2x4=8
44x31233x412
Wecanthenaddthesetwofractionsdirectly:
1+2=3+8=3+8=11
4312121212
Eg:
2+1=?
56
2=2x6=121=1x5=5
55x63066x530
2+1=12+5=12+5=17
5630303030
SubtractingFractions
Thisworksinthesamewayasaddition.Ifthedenominatorsarethesame,simplysubtractalongthetopline:
5-3=5–3=2=1x2=1
66663x23
12-1=12-3x1=12-3=12–3=9
155153x515151515
Cancellingdowngives9=3x3=3
153x55
NB:
analternativemethodwouldhavebeentocanceldown12/15to4/5initiallyleavinganeasiersumof4/5–1/5=3/5
MultiplicationofFractions
Itmayhelptounderstandmultiplicationifyouinterpretthe‘x’signas‘of’.
Hence:
1x2means1of2=1
25255
Thecalculationinvolvesmultiplyingbothnumeratorsandbothdenominatorsthencancellingdown:
Eg:
1x2=1x2=21=1
252x51055
4x2=4x2=8
535x315
7x3=7x3=21
11811x888
Notethatwhenmultiplying,youcancanceldownduringthesumaswellasatthefinalstage–itoftenmakesthecalculationeasier:
Eg:
31x2=2
133113
41x3=1x31=1x1=1
982932326
5x61=5x1=5
24474x728
DividingFractions
Thetrickwithdivisionoffractionsistoturnthesecondfractionupsidedownandthentomultiply:
Eg.21=2x5=10
35313
Notethatthisanswercanalsobewrittenas31/3
24=21x5=5
7574214
27=2x8=16
383721
ImproperFractions
Animproperfractionisonewherethenumeratorislargerthanthedenominator,eg.10/3
Toconvertthistoamixednumber(onecombiningawholenumberandafraction),thinkof10/3inthefollowingway:
1
3
3x1/3=1sooutoftheten1/3’s,ninecanbegroupedintothreewholeunits,leavingonly1/3leftover.Hence,10/3=31/3
Similarly,12/5=22/5
16/11=15/11
21/15=16/15=12/5(bycancelling)
Wecanalsogofrommixednumberstoimproperfractions:
21/8=(2x8)+1=16+1=17
88888
31/4=(3x4)+1=12+1=13
44444
Additionofmixednumbers
Eg.2½+31/5=2+3+½+1/5
=5+5/10+2/10
=5+7/10
=57/10
17/8+52/3=1+5+7/8+2/3
=6+21/24+16/24
=6+37/24
=6+113/24
=713/24
MultiplicationandDivisionofmixednumbers
Here,itisusuallyeasiesttoconverttoimproperfractionsandmultiplyordivideasnormal:
Eg:
25/6x31/8=17/6x25/8=425/48=841/48
12/32¾=5/311/4=5/3x4/11=20/33
2½x41/31¼=5/2x13/35/4=5/2x13/3x4/5=260/30=26/3=82/3
Nowtrytheseexamples:
Notethatinthesequestions2/5isthesameas2
5
1.2/5+1/32.7/8–1/53.5/8+2/34.2/9+4/11
5.6/7–4/96.7/8–1/37.2½-15/88.7¼-52/3
9.24/5+67/810.2/3x4/511.8/9x1/312.7/12x4/5
13.8/92/314.2/114/515.6/79/816.2¼x3½
17.51/7x21/518.3
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 教你如何作笔试题math centre Numeracy大型外企业笔试必备 如何 笔试 math Numeracy 大型 外企 必备