$A$ radioactive substance has a half-life of $h$ days. Its initial decay rate is given by (where the radioactive substance has an initial mass $m_0$).

$A$ tangent is drawn at any point $P(x, y)$ on a curve, which passes through $(1, 1)$. The tangent cuts the $X$-axis and $Y$-axis at $A$ and $B$ respectively. If $AP:BP = 3:1$, then:

Let $f$ be a non-negative function defined in $[0, \pi / 2]$, $f^{\prime}$ exists and is continuous for all $x$, and $\int_0^x \sqrt{1-\left(f^{\prime}(t)\right)^2} dt = \int_0^x f(t) dt$ with $f(0) = 0$. Then

The differential equation $y\frac{dy}{dx} + x = a$ ($a$ is any constant) represents:

The money invested in a company is compounded continuously. If ₹ $400$ invested today becomes ₹ $800$ in $6$ years,then at the end of $30$ years,it will become (in ₹)

The rate at which a substance cools in moving air is proportional to the difference between the temperature of the substance and that of air. The temperature of air is $290 \ K$ and the substance cools from $370 \ K$ to $330 \ K$ in $10 \ minutes$. Then the time to cool the substance up to $295 \ K$ is: (in $min$)