A radioactive isotope has a half-life of one month. At the end of one month, the amount of the original isotope still remaining is
1) none,
2) one-quarter,
3) one-half,
4) three-fourths,
and at the end of two months, the amount of original isotope remaining is
5) none.
6) one-fourth.
7) one-half.
8) three-fourths.
Answer: 3, 6
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Fill in the blank(s) with correct word
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What is thought to be the origin of enormous x-ray flares that occasionally come from the direction of Sgr A*?
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Based on our current Gregorian calendar, which of the following years is not a leap year?
A) 2000 B) 2004 C) 2008 D) 2012 E) All of the above are leap years.