Multiple choice general knowledge science & technology

There is 1 gram of radioactive radium with a half-life period of 5 min. After 15 min how much radium is left?

  1. .125 gram

  2. .5 gram

  3. .25 garm

  4. 1 gram
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

After 15 minutes, exactly 3 half-lives have passed (15/5 = 3). Each half-life reduces the amount by half, so after 3 half-lives: 1 gram * (1/2)^3 = 1 * 1/8 = 0.125 gram remains.

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