boomgoesthegmat wrote:Which of the following is the value of squareroot[cuberoot(0.000064)]?
A) 0.004
B) 0.008
C) 0.02
D) 0.04
E) 0.2
To solve this question, we can refer to two rules:
1) If a decimal with a finite number of decimal places is a perfect cube, its cube root will have exactly one-third of the number of decimal places. Thus, a perfect cube decimal must have a number of decimal places that is a multiple of 3.
2) If a decimal with a finite number of decimal places is a perfect square, its square root will have exactly half of the number of decimal places. Thus, a perfect square decimal must have an even number of decimal places.
Let's look first at cuberoot(0.000064). By rule number 1, the cube root of 0.000064 = 0.04. We were able obtain this value because 0.000064 has 6 DECIMAL PLACES, and because the cube root of 64 is 4.
The problem now looks like this: squareroot(0.04). By rule number 2, the square root of 0.04 = 0.2. We were able to obtain this value because 0.04 has 2 DECIMAL PLACES, and the square root of 4 is 2.
Alternate Solution:
First, we note that taking the cube root of the square root of a number is equivalent to taking the sixth root of the number.
Next, let's write 0.000064 = 64/1000000 = 2^6/10^6. Taking sixth root, we obtain 2/10 = 0.2.
Answer:
E
