UPSC NDA I 2021 General Ability Solved Paper

The correct answer is 75 degrees W . Longitude. Key Points Finding Direction: $\Rightarrow$ Current time in India $=12:00\ \text{p}\cdot\text{m}$. $\Rightarrow$ Time at required meridian $=7:00$ a.m. $\Rightarrow$ Difference in time $=5\ \text{hrs}$, and thistime at meridian $(7:00\ \text{a} . \text{m} .$ ) is $5\ \text{hrs}$ behind. Hence it is west direction. Note: When time on a meridian is lagging with respect to the time of others, then it lies to the west. Calculation of Longitude: As we know the Earth takes $24\ \text{hrs}$.for one complete rotation, so $\Rightarrow 24\ \text{hrs} .=360^{\circ}$ $\Rightarrow 1\ \text{hr}=\;\frac{360}{24}=15^{\circ}$, thus the Earth rotates $1\ 5$ degrees in $1\ h\ r$. $\Rightarrow \;\; \;\text{ In }\; 5\ \text{hrs}=5 \times 15^{\circ}=75^{\circ}$ Hence at $7\ 5^{\circ}$ West longitude, the time will be $7:00\ \text{a}.\text{m}.$