Big Book Test 3 section 6 Q20

GRE Quant Problem Solving
1

Hello! This is an easy problem but I am having difficulty finding the right answer. What I am doing is simplifying square root of 0.25r^6 to 0.25^4 but then non of the answer choices make sense.

  1. If r > 0, then square root of 0.25r^6 =
    (A) 0.05r ^3
    (B) 0.05r^4
    (C) 0.05r^5
    (D) 0.5r^2
    (E) 0.5r^3
2

Substitute r =2, then 0.25r^6 = 0.25 x 64 = 16, sqrt of 16 = 4.
Substitute r =2 in option E, 0.5r^3 = 0.5 x 8 = 4
Therefore answer is option E.

Another way
sqrt(0.25) = 0.5 and sqrt(r^6) = r^3
so answer is 0.5xr^3