• # question_answer Case Study : Q. 6 to 10 Sanjeev a student of class X, goes to Yamuna river with his friends. When he saw a boat in the river, then he wants to sit in boat. So his all friends are ready to sit with him. In this order, Sanjeev is sitting on a boat which upstream at a speed of $\text{8 km}/\text{h}$ and downstream at a speed of$\text{16 km}/\text{h}$. When Sanjeev is in the boat, some questions are arises in the mind, then answer the given questions. The speed of the boat in still water is: A) $\text{8 km}/\text{h}$ B) $\text{1}0\text{ km}/\text{h}$ C) $\text{12 km}/\text{h}$ D) $\text{14 km}/\text{h}$

 Let the speed of the boat in still water be $x\,\,km/h$and speed of the stream be $y\,\,km/h$ Then,                $x-y=6$                         ...(1) $x+y=14$                          ...(2) On adding eqs. (1) and (2), we get $2x=20$ $\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x=10$ $\therefore$   Speed of the boat in still water is $\text{1}0\text{ km}/\text{h}$ So, option [b] is correct.