Question

An aeroplane is moving at a constant altitude 'h'. At 10:00 AM, it is seen at an elevation of 30°. 1 minute later, it is observed at an elevation of 60°. If the speed of the plane is 960 km/h, then find 'h'.

• A. 13.86 km
• B. 15 km
• C. 12.46 km
• D. 20 km

Answer 1

Answer:

A. 13.86 km

Distance traveled

$=\frac{960}{60}=16 km$

$d_1-d_2=16km$

$tan 30 = \frac{h}{d_1} \Rightarrow d_1=\frac{h}{tan30}$

$tan 60 = \frac{h}{d_2} \Rightarrow d_2=\frac{h}{tan60}$.

$=\frac{h}{tan30}-\frac{h}{tan60}$

$=\frac{h}{\frac{1}{\sqrt3}}-\frac{h}{\sqrt3}=16$

$=h=8\sqrt3=13.85 km$