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MHT CET · Maths · Differential Equations

Bismath has half life of 5 days. If sample originally has a mass of \(800 \mathrm{mg}\). then the mass remaining after 30 days will be

  1. A \(10 \mathrm{mg} .\)
  2. B \(10.5 \mathrm{mg} .\)
  3. C \(12 \mathrm{mg} .\)
  4. D \(12.5 \mathrm{mg} .\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(12.5 \mathrm{mg} .\)

Step-by-step Solution

Detailed explanation

Original mass \(=800 \mathrm{mg}\).
Half life \(=5\) days.
We have to calculate remaining mass after 30 days. Understand that \(30 \div 5=6\).
\(\begin{aligned} \therefore \text { Mass remaining } &=\left(\frac{1}{2}\right)^{6} \times 800 \\ &=\frac{800}{64}=\frac{100}{8}=12.5 \end{aligned}\)