A boat travels 12 km upstream and back in total time of 1 hr and 15 minutes. When there's constant current speed is 1.5 km/h, find speed of the boat in still water.

Question

baru · Answer

$t_1$: time taken for upstream travel
$t_2$:time taken for downstream travel

speed of boat: s
downstream speed: s+1.5
upstream speed s-1.5
$t_1=12/(s-1.5)\t_2=12/(s+1.5)$

$t_1+t_2= 1hr15min$

anonymous · Answer

you calculated how to find speeds in downstream and upstream, but what about speed in still water?

baru · Answer

i have not calculated anything...I have left the last step for you to solve.
just substitute $t_1~and~t_2$ into the last equation. solve for "s" 
s is the speed of boat in still water

anonymous · Answer

Right. Thanks a lot for the help! :)