Rakesh starts walking from his house and then takes two left turns and one right turn to reach the market. If he is facing north on reaching the market, in which direction was Rakesh facing when he started from his house?
Explanation:
Let's analyze the net effect of the turns. A left turn corresponds to a $-90^\circ$ rotation (counter-clockwise), and a right turn corresponds to a $+90^\circ$ rotation (clockwise). \nRakesh takes two left turns and one right turn:\nNet rotation $= (-90^\circ) + (-90^\circ) + (+90^\circ) = -90^\circ$. \nThis means the final direction is $90^\circ$ counter-clockwise from the starting direction.\nLet $D_S$ be the starting direction and $D_F$ be the final direction. $D_F = D_S - 90^\circ$ (counter-clockwise). \nWe are given that $D_F = \text{North}$. To find $D_S$, we reverse the operation: $D_S = D_F + 90^\circ$ (clockwise). $D_S = \text{North} + 90^\circ \text{ (clockwise)}$. $D_S = \text{East}$. \nLet's verify:\nIf Rakesh started facing East: 1. Started East. 2. First Left Turn: East $- 90^\circ = \text{North}$. 3. Second Left Turn: North $- 90^\circ = \text{West}$. 4. One Right Turn: West $+ 90^\circ = \text{North}$.\nThis matches the final direction given in the problem. \nOption (A) North: If Rakesh started North, he would end up West (North $\xrightarrow{L}$ West $\xrightarrow{L}$ South $\xrightarrow{R}$ West). This is incorrect.\nOption (B) South: If Rakesh started South, he would end up East (South $\xrightarrow{L}$ East $\xrightarrow{L}$ North $\xrightarrow{R}$ East). This is incorrect.\nOption (C) East: As derived, if Rakesh started East, he would end up North. This is the correct option.\nOption (D) West: If Rakesh started West, he would end up South (West $\xrightarrow{L}$ South $\xrightarrow{L}$ East $\xrightarrow{R}$ South). This is incorrect.