3 km
Speed downstream = \( 5 + 1 = 6 \) km/h, upstream = \( 5 - 1 = 4 \) km/h.
Let distance to place = \( d \) km. Total time = 1 hour:
\[ \frac{d}{6} + \frac{d}{4} = 1 \] \[ \frac{2d}{12} + \frac{3d}{12} = 1 \Rightarrow \frac{5d}{12} = 1 \Rightarrow d = \frac{12}{5} = 2.4 \] Thus, the answer is 2.4 km.
A boat travels 36 km downstream in 3 hours and 24 km upstream in 3 hours. What is the speed of the boat in still water?
What is the sum of digits of $2^{10}$?