$$ \text { The area of the region (in square units) bounded by the line } y+3=x ; x=1 \text { and } x=5 \text { is } $$
If an ellipse has an equation in the standard form and it passes through the points $$\left(\frac{5}{2}, \frac{\sqrt{6}}{4}\right)$$ and $$\left(-2, \frac{\sqrt{15}}{5}\right)$$ then the length of its latus rectum is
A transformer has 400 turns in its primary winding and 800 turns in its secondary winding. The primary voltage is $$20 \mathrm{~V}$$ and the load in the secondary is 4 ohm. The current in the primary, assuming it to be an ideal transformer, is
An object is placed at a distance of $$12 \mathrm{~cm}$$ from a convex lens on its principal axis and a virtual image of certain size is formed. If the object is moved $$4 \mathrm{~cm}$$ away from the lens, a real image of the same size as that of the virtual image is formed. The focal length of the lens in $$\mathrm{cm}$$ is