Symbiosis National Aptitude Test SNAP 2012 Paper

Let the aeroplane covers x km at a speed of 440 km/h and (x – 770) km at a speed of 660 km/h.
Hence, it covers a total distance of (2x – 770) km at a speed of 500 km/h.

Average speed = $\frac{\mathrm{Total}\mathrm{distance}}{\mathrm{Total}\mathrm{time}}$
⇒ 500 = $\frac{2\mathit{x}-770}{\frac{\mathit{x}}{440}+\frac{\mathit{x}-770}{660}}$
or $\frac{2\mathit{x}-770}{500}$ = $\frac{\mathit{x}}{440}+\frac{\mathit{x}-770}{660}$
or x = 1760
Therefore, the total distance covered = 2x – 770
= 2 × 1760 – 770 = 2750 km