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MHT CET · Maths · Differential Equations

Radium decompose at the rate proportional to the amount present at any time. If \(\mathrm{P} \%\) of amount disappears in one year, then amount of radium left after 2 years is

  1. A \(\left(10-\frac{P}{10}\right)^2\)
  2. B \(x_0\left[1+\frac{P}{100}\right]^2\)
  3. C \(x_0\left[1-\frac{P}{100}\right]^2\)
  4. D \(x_0\left[10-\frac{P}{100}\right]^2\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(x_0\left[1-\frac{P}{100}\right]^2\)

Step-by-step Solution

Detailed explanation

\(\mathrm{P} \%\) amount disappears in one year.
Let initial amount of radium \(=\mathrm{x}_0\)
\(\therefore\) Amount left after 1 year \(=\mathrm{x}_0-\frac{\mathrm{P}}{100} \times \mathrm{x}_0=\mathrm{x}_0\left(1-\frac{\mathrm{P}}{100}\right)\)
Amount left after 2 years
\(
\begin{aligned}
& =x_0\left(1-\frac{P}{100}\right)-\frac{P}{100} \times x_0\left(1-\frac{P}{100}\right) \\
& =x_0\left(1-\frac{P}{100}\right)\left(1-\frac{P}{100}\right)=x_0\left(1-\frac{P}{100}\right)^2
\end{aligned}
\)