Problem:
When the decimal point of a certain positive decimal number is moved four places to the right, the new number is four times the reciprocal of the original number. What is the original number?
Answer Choices:
A.
B.
C.
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E.
Solution:
If is the number, then moving the decimal point four places to the right is the same as multiplying by . That is, , which is equivalent to . Since is positive, it follows that .
Answer: .
The problems on this page are the property of the MAA's American Mathematics Competitions