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# I am posting the good ones for your practice.. Trying to

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Senior Manager
Joined: 20 Feb 2006
Posts: 331
I am posting the good ones for your practice.. Trying to [#permalink]

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03 Jul 2006, 19:24
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

I am posting the good ones for your practice..

Trying to solve these in less than 2 mins.. It can be quite a challenge when 2 or more answers are close as seen in following example..

5. The length of an edge of cube A is 5% greater than the length of an edge of cube B. If the volume of cube B is 27 cubic centimeters, then what is nearest to the volume of cube A?

(A) 23.1
(B) 25.65
(C) 27.125
(D) 28.35
(E) 31.25
Manager
Joined: 12 Apr 2006
Posts: 215
Location: India

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03 Jul 2006, 21:32
(E) 31.25 in less than 1 minute
CEO
Joined: 20 Nov 2005
Posts: 2894
Schools: Completed at SAID BUSINESS SCHOOL, OXFORD - Class of 2008

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03 Jul 2006, 21:40
(a+b)^3 = a^3+b^3+3ab^2+3ba^2

Ignore b^3 and 3ab^2 because values of b^3 and b^2 will be smaller and here we need to find only upto two decimals.

(3+0.05)^3 = 27+Ignore+Ignore+3*0.05*9 = 27+1.35 = 28.35

I solved it in less than a minute.
_________________

SAID BUSINESS SCHOOL, OXFORD - MBA CLASS OF 2008

Senior Manager
Joined: 08 Jun 2004
Posts: 495
Location: Europe

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03 Jul 2006, 22:50
'E' it is 31.25 less then 1 minute.

Side lenth of B = 3 cm.
Side lenth of A = that of B + 5% = 3.15 cm.
Volume of A = 3.15^3 = 31.25

Hope it is clear.
SVP
Joined: 30 Mar 2006
Posts: 1728

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03 Jul 2006, 23:08
ps_dahiya wrote:
(a+b)^3 = a^3+b^3+3ab^2+3ba^2

Ignore b^3 and 3ab^2 because values of b^3 and b^2 will be smaller and here we need to find only upto two decimals.

(3+0.05)^3 = 27+Ignore+Ignore+3*0.05*9 = 27+1.35 = 28.35

I solved it in less than a minute.

E for me too.

Dahiya....... it should be .15. 5 % of 3 is .15........ I know it bugs every body when we make such mistakes.
CEO
Joined: 20 Nov 2005
Posts: 2894
Schools: Completed at SAID BUSINESS SCHOOL, OXFORD - Class of 2008

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03 Jul 2006, 23:50
jaynayak wrote:
ps_dahiya wrote:
(a+b)^3 = a^3+b^3+3ab^2+3ba^2

Ignore b^3 and 3ab^2 because values of b^3 and b^2 will be smaller and here we need to find only upto two decimals.

(3+0.05)^3 = 27+Ignore+Ignore+3*0.05*9 = 27+1.35 = 28.35

I solved it in less than a minute.

E for me too.

Dahiya....... it should be .15. 5 % of 3 is .15........ I know it bugs every body when we make such mistakes.

These mistakes gonna kill me....
_________________

SAID BUSINESS SCHOOL, OXFORD - MBA CLASS OF 2008

03 Jul 2006, 23:50
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