k so im doing some study questions for SAT cuz i have to take it soon.. and i dont understand the answer to this question:
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9. If x is an integer, which of the following could be x³?
I 1.25 x 1017
II 12.5 x 10-12
III 0.125 x 10-12
A. I only
B. II only
C. I and II only
D. I and III only
E. II and III only
Correct Answer: D
Explanation:
We can shift the decimal points so that we get 125 and a power of ten. 125 is a cube. If the power to which ten is raised is divisible by 3, then that is also a cube.
For statement I we get 125 x 1015 (We have multiplied the 1.25 by 100 and so we must divide 1017 by 100 which means we subtract 2 from the power). For statement II we get 125 x 10-13, and for III we get 125 x 10-15. Only in the case of I and III is the power divisible by three.
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http://www.majortests.com/sat/explain.php?exp=503031312439243436
It said if x is an integer, meaning a whole number? So that would mean the answer would be A, because the cube root of choice III is 5x10^-5 (or 0.00005). And that number is not an integer :|
Anyone have any ideas? I know this is a lame topic to start a thread about, especially on a tennis forum, but i need a good SAT math score lol cuz my english is ****ty