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Question Number 78937 by mr W last updated on 21/Jan/20

Commented by mr W last updated on 21/Jan/20

As shown, the areas of three parts of  a rectangle are given. Find the area  of the fourth part.

Asshown,theareasofthreepartsofarectanglearegiven.Findtheareaofthefourthpart.

Commented by john santu last updated on 22/Jan/20

the Area is required =   (√((A+B+C)^2 −4AC))

theAreaisrequired=(A+B+C)24AC

Commented by john santu last updated on 22/Jan/20

that right sir?

thatrightsir?

Commented by mr W last updated on 22/Jan/20

no sir!  correct result see solution below from  ajfour sir. it is (√((A+B+C)^2 −4AB)).

nosir!correctresultseesolutionbelowfromajfoursir.itis(A+B+C)24AB.

Commented by john santu last updated on 22/Jan/20

oo yes. i′m wrong to calculate

ooyes.imwrongtocalculate

Answered by ajfour last updated on 21/Jan/20

let rectangle length=a+c  height=b+d  2B=(a+c)b  2A=(b+d)a  2C=cd  let  ?=Q  Q=(a+c)(b+d)−(A+B+C)     = ((4AB)/(ab))−(A+B+C)  (2B−ab)(2A−ab)=2Cab  (ab)^2 −2(A+B+C)(ab)+4AB=0  ab=(A+B+C)−(√((A+B+C)^2 −4AB))  hence  Q=((4AB)/((A+B+C)−(√((A+B+C)^2 −4AB))))−(A+B+C)

letrectanglelength=a+cheight=b+d2B=(a+c)b2A=(b+d)a2C=cdlet?=QQ=(a+c)(b+d)(A+B+C)=4ABab(A+B+C)(2Bab)(2Aab)=2Cab(ab)22(A+B+C)(ab)+4AB=0ab=(A+B+C)(A+B+C)24ABhenceQ=4AB(A+B+C)(A+B+C)24AB(A+B+C)

Commented by mr W last updated on 22/Jan/20

thank you sir! perfect!  the last line can be simplified to  Q=(√((A+B+C)^2 −4AB))

thankyousir!perfect!thelastlinecanbesimplifiedtoQ=(A+B+C)24AB

Commented by mr W last updated on 22/Jan/20

+ sign is suitable, since ab>A+B+C  ab=(A+B+C)+(√((A+B+C)^2 −4AB))

+signissuitable,sinceab>A+B+Cab=(A+B+C)+(A+B+C)24AB

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