| 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. |
 |
A) \[\text{8 km}/\text{h}\]
B) \[\text{1}0\text{ km}/\text{h}\]
C) \[\text{12 km}/\text{h}\]
D) \[\text{14 km}/\text{h}\]
Correct Answer: B
Solution :
| 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. |
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