X^4+Y^4=100

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gmatmachoman: Legendary Member; Posts: 2326; Joined: Mon Jul 28, 2008 3:54 amFollowed by: 2 members; Thanked: 173 times; GMAT Score:710

by gmatmachoman » Sun Feb 14, 2010 2:24 am

11. If X^4+Y^4=100, then the greatest possible value of X is between:

A. 0 and 3
B. 3 and 6
C. 6 and 9
D. 9 and 12
E. 12 and 15

R&D on GMAT algorithm:

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ajith: Legendary Member; Posts: 1275; Joined: Thu Sep 21, 2006 11:13 pmFollowed by: 2 members; Location: Arabian Sea; Thanked: 125 times

by ajith » Sun Feb 14, 2010 2:36 am

gmatmachoman wrote:11. If X^4+Y^4=100, then the greatest possible value of X is between:

A. 0 and 3
B. 3 and 6
C. 6 and 9
D. 9 and 12
E. 12 and 15

Please use search

https://www.beatthegmat.com/x-4-y-4-100-t46238.html

Always borrow money from a pessimist, he doesn't expect to be paid back.

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komal: Legendary Member; Posts: 777; Joined: Fri Jan 01, 2010 4:02 amFollowed by: 47 members; Location: Mumbai, India; Thanked: 117 times

by komal » Tue Feb 16, 2010 9:18 am

gmatmachoman wrote:11. If X^4+Y^4=100, then the greatest possible value of X is between:

A. 0 and 3
B. 3 and 6
C. 6 and 9
D. 9 and 12
E. 12 and 15

If y^4 is 0 then x^4 will be the greatest = > x will be greatest
Hence x^4 =100 ; x will be between 3 ( 3^4= 81)and 4.
Hence, answer is B.

https://www.e-gmat.com/

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8183; Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members; Location: Los Angeles, CA; Thanked: 43 times

by Scott@TargetTestPrep » Tue Dec 12, 2017 10:20 am

gmatmachoman wrote:11. If X^4+Y^4=100, then the greatest possible value of X is between:

A. 0 and 3
B. 3 and 6
C. 6 and 9
D. 9 and 12
E. 12 and 15

In determining the greatest possible value of x, we want to minimize y^4. Since the minimum value of y^4 is 0 (when y = 0), we have:

x^4 + 0 = 100

x^4 = 100

x^2 = 10

x = +/-âˆš10

x â‰ˆ 3.2 or -3.2

Thus, we see that the greatest value of x is between 3 and 6.

Answer: B

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