Jack sailed his boat 128 km down a river in the same time it took to travel 112 km up the river.His speed down
915164
128 / ( x + 4 ) = 112 / x\n128 x = 112 ( x + 4 ) = 112 x + 448\n16 x = 448\nx = 28 km/hr upriver and x + 4 = 32 km/hr downriver
518996
He has to drive two miles (one mile up and one mile down) in two minutes.  He already took two minutes to get up the hill, so it is impossible for him to average 60 mph.
874038
hope you find this useful....\nconsider instead of a round trip, he takes a trip in only one direction, from say A to B....i.e for 360 miles\nas you know, \nspeed = distance/time  or   time = distance/speed\n\nso , with constant speed say x, his time t  is 360/x.\n\nconsidering any point m between A and B, his total time  for the journey can also be written as the sum of the time taken from A to m, and time taken from m to B.\n\n t = 360/x = [m/x ]+ [( 360- m )/x ] ---------(1) \n\nthis is a general solution ,considering the trip as being in only one direction. but in our problem, the journey is up and down,so  the point m is midway (180),and his speed changes ( increases by 9)his total time changes(given as decreases by 2 hours).\n\nso the new equation is....\n\nt-2 = [m/x ]+ [(360 - m)/(x+9)]     ---------(2)\n\nsubtracting (2) from (1), we get,\n\nt - (t-2) =[ (360 -m)/x ] -  [ (360 -m)/(x+9)]-----------(3)\n\n 2 = [180/x] - [ 180/(x+9)]...........( since m = 180)\n\nsolve for x...\n\nthats the speed in the forward trip\nx+9 is the speed on the return trip.
143101
speed is distance divided by time. So work out the distance the water needs to travel and divide by the time taken. Add more details if you want to know a more complex way to work out the speed.
303745
54 mi in 3 hours is a speed of 18mph (54/3=18),\n54 mi in 3.6 hours is a speed of 15mph (54/3.6=15),\nTHe current is half the difference between the two - it helps as much as it stops you....\nTherefore current is 1.5mph ((18-15)/2=1.5) and the boatspeed in calm water is 16.5mph (15+1.5 or 18-1.5).\n\nThe equations are, with boat rate=x and current=c;\nx+c=18      (1)\nx-c=15      (2)\n(1) ==> c=18-x\ninsert c into (2) ==> x-18+x=15\n==>2x=33 ==>x=33/2=16.5\nInsert x into (1) or (2) to get c=1.5   \n\nHope it helps,\nFredrik, MSc
1057721
The probability = 1 (100%)\nThat's pretty simple, but it's more of a riddle than a probability question. I think you knew that.(There might not be any trees or plants, but we know what you mean.)\nIt doesn't matter whether he walks at a constant velocity coming or going (He can speed up and slow down, as long as he makes the trip in 12 hrs.) He will be at exactly the same place at the same time as the day before, once. This is easily understood if, intsead, you imagine one man starting from the bottom and another man from the top. They have to meet, and when they do they will be at the same spot at the same time. It's irrelevant that it's the same man (a day apart).
370194
its 225 mph or 362 kmph
1111831
We finished the race at a record breaking speed of\n\n1'40"89.  For more on this contest see:\nhttp://www.tc.umn.edu/~mcsa/new/picalbum/dragon/afterdragonboat.htm\n\nSpeed records vary with each race, and records are being broken as we speak.\nSee what they have to say at:\nhttp://www.dragonboat.org.uk/
831793
1.200/x-200/(x+10)=1\n200(x+10)-200x=x(x+10)\n200x+2000-200x=x^2+10x\nx^2+10x-2000=0\n(x+50)(x-40)=0\nx=-50 or 40\nignoring the negative value x=40\noriginal speed of the car=40mph\n\n2.60/(x+3)+60/(x-3)=9\n\n60(x-3)+60(x+3)=9(x^2-9)\n120x=9x^2-81\n9x^2-120x-81=0\nx=[120+/-rt(14400+2916)]/18\n=120+131.6/18=14 approximately\nspeed of boat in still water =14 mph\n\n3.x^2+24=(x+1)^2-25\n(x+!)^2-x^2=49\n2x+1=49\n2x=48\nx=24\nno of characters=576+24=600
382187
1.022 km/s so 3679.2km/h
812527
the answer is 125 mi/hr
475019
It's about 340.46464663663662662 nautical miles.
379715
A canal is man-made, a river is natural.
981265
Call the speed the kayaker would make in still water x (mph).\n\nWhen he paddled with the current, the actual speed of the kayak was x+6.\n\nWhen he paddled against the current, the actual speed of the kayak was x-6.\n\nSince the lengths of both trips are the same, we have:\n2*(x+6) = 3*(x-6) <-> 2x + 12 = 3x - 18 <-> x = 30.\n\nHe would manage 30mph in still water (wow, what a beast :)))
287822
There are sections of the river (in Quebec) where the tides cause the river to flow upstream.  This still happens today.
1052912
Noone will state at this time, but I found this:\n\n"He was sailing, like he was enjoying the ride. He was going at a good clip but wasn't going overly fast," Ms. Ford said.
859226
He actually took 127 years building the boat.  It wasn't a waste of time other than his ministry to the unsaved, who never took his warnings. He wasn't a drinker, where did u hear that?