nevermind.. it was my bad :)

[bfman]

Referencing Official Guide 12th Edition. Page 197 Q 32.

Both B and D are correct depending on how to solve the root.
What's the deal?

[raleigh]

sqrt[(16)(20) + (8)(32)] =
sqrt[ (2^4)(5*2^2) + (2^3)(2^5)] =
sqrt[5*2^6 + 2^8] =
sqrt[2^6(5 + 2^2)] =
sqrt[2^6]*sqrt[5 + 2^2] =
8*sqrt[9] =
8*3 =
24

You broke some rule of algebra if you got D. Solving a problem in different way must yield the same answer. How did you get D?

[bfman]

sqrt[(16)(20) + (8)(32)]

sqrt[ 16*20 ] + sqrt[ 8*32 ]

sqrt[ (2^4) * (4*5) ] + sqrt[ (2^3) * (2^5) ]

4sqrt[20] + 8sqrt[2] <--- This is answer D

[bfman]

Ok my bad. I guess I'm not suppose to separate roots like that.. LoL

[raleigh]

You can ONLY split a root under MULTIPLICATION/DIVISION. The GMAT will always tempt you to split a root on addition/subtraction.

[bfman]

Thanks