Multiple choice

The half life of a substance is 10 days. If the initial mass is 2 g, how much of the substance will be left after 40 days?

  1. 0.0125 g

  2. 0.125 g

  3. 0.5 g

  4. 1.25 g
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

After 40 days (which is 4 half-lives of 10 days each), the remaining mass = 2g × (1/2)^4 = 2g × 1/16 = 0.125g. Each half-life reduces the quantity by half, so after n half-lives, remaining = initial × (1/2)^n.

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