GMAT prep problem

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sumatitandon: Junior | Next Rank: 30 Posts; Posts: 13; Joined: Fri Oct 17, 2008 3:06 am; Location: singapore

by sumatitandon » Fri Jan 09, 2009 2:57 am

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

Source: Beat The GMAT — Problem Solving | Fri Jan 09, 2009 2:57 am

piyush_nitt: Master | Next Rank: 500 Posts; Posts: 424; Joined: Sun Dec 07, 2008 5:15 pm; Location: Sydney; Thanked: 12 times

by piyush_nitt » Fri Jan 09, 2009 3:03 am

sumatitandon wrote: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

IMO B

Value of X will be maximum when Y = 0

therefore x^4 = 100

3. something ..

therefore value of X should lie between 3 and 6

welcome: Master | Next Rank: 500 Posts; Posts: 137; Joined: Thu Jan 08, 2009 1:27 am; Thanked: 7 times

by welcome » Fri Jan 09, 2009 3:05 am

To make X max, make Y to minimum that will be zero(Cant be -ve and power is even).
Value to x will be b/w 3 to 6 to make it between 100.

Answer B.

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