Three circles of radius a, b, c touch each other externally. The area of the triangle formed by joining their centres is

P owns 2/3 shares of a company and the rest of the shares is equally divided among Q and R. If the profit on each share increases from 5% to 7%, P earns an extra 800 rupees. The investment of R on the shares is

Three bells ring simultaneously at 11 a.m. They ring at regular intervals of 20 minutes, 30 minutes, 40 minutes respectively. The time when all the three ring together next is

If $$\frac{a}{b} = \frac{c}{d} = \frac{e}{f} = 3$$, then $$\frac{2a^2 + 3c^2 + 4e^2}{2b^2 + 3d^2 +4f^2}$$ = ?

Evaluate : 3 cos 80° cosec 10° + 2 cos 59° cosec 31°