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moonlite: Senior | Next Rank: 100 Posts; Posts: 61; Joined: Fri Jun 06, 2008 5:58 am; Thanked: 1 times

by moonlite » Tue Apr 28, 2009 4:52 am

Can someone please help me solve this?

Thanks.

√[2√63 + 2/(8+3√7)] =

A. 8 + 3√7
B. 4 + 3√7
C. 8
D. 4
E. √7

OA D

Source: Beat The GMAT — Problem Solving | Tue Apr 28, 2009 4:52 am

sacx: Master | Next Rank: 500 Posts; Posts: 139; Joined: Wed Oct 22, 2008 4:36 am; Thanked: 17 times

by sacx » Tue Apr 28, 2009 5:11 am

√[2√63 + 2/(8+3√7)]

= √[6√7 + 2/(8+3√7)]
= √2[3√7 + 1/(8+3√7)]
= √2[(24√7+63 + 1)/(8+3√7)]
=√2[(24√7+64)/(8+3√7)]
=√16[(3√7+8)/(8+3√7)]
= 4

SACX

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