Algebra Foundation Quiz #2 Q7

GRE Quant Problem Solving
1

If you double the reciprocal of a certain positive number eight times, the result is the cube of the number. What is the number?

the answer is 4 how is it solved?

2

Let’s say the number equals x. The reciprocal would be 1/x. If you double this eight times you get:
2/x
4/x
8/x
16/x
32/x
64/x
128/x
256/x

We know that this equals x^3 so we can set them equal to each other.
256/x=x^3

Now we can multiply by x to get
256=x^4

Now we can take the fourth root of 256.

The fourth root of 256=4

Hope this helps.

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