Hi friends. This is the problem based on a concept off crossing the river. Here it is given there is a river having the bit 400 m in which water current is a bit off. The river is 400 m, in which water current is 30 meter permanent. American wrote about Britain maximum speed off 100 meter bit permanent with respect of water in Stillwater. It starts from the 0.8 on the South Bank on the north. Make There is a point we just vertically ever on down to the point we there is a point. C on B. C is given 75 m in the part eight. This is the south. This is the not the it on north sore. Will you lend if you point right point your boat perpendicular toe water flow on calculate distance covered. Let us see the solution for what? Ruin perpendicular toe flow off water Crossing his speed is 100 m per minute and drifted speed down to the street as 30 m permanent. Hence time taken by the boat to reach downstream. So time off crossing the river, you will get distance based off the river upon crossing speed. So time off crossing you will get 400 divided by 100. That is four minute and during the four minute drifted, it will be on. It will reach from 3.2 d. You can mark in the figure. Just a moment. So what will reach at pointy, which is video distance of it Drifted speed in tow. Crossing time drifted spirits 30 m Permanent time is four minutes. That is one contributor. So what will reach down to dusting? One contributor from B and total distance covered will be B D square plus a V script. Yeah, I am growing the diagram here. This is the river. This is the water float. This is the point A on the South Bank. And this is the point. We on the North Bank he's rowing the boat in this direction So he will reach here on the distance Covered will be equal to 80 so that we're measuring so distance as which is equal to every so you can measure by Pythagoras So BD we a major 1 20 a d is 400 So total distance 400 17.6 m. This is the answer apart ape in part we if you a your boat and usually the watch. See? We're on the north. You will let then? Yeah. On the north you lend. Let us see the diagram. This is the worst of the river indeed. As you know, 400 m, this is the flow of water. This is the south bank of the river at eight. This is the north. Make a V. The 60 point on B c A B is 400 m. We see it 75 m. You are aiming the boat to raw along this easy like so this angle will with theater. Yeah, so drift velocity. So the crossing speed will be we cause of theater and it would be 100 in tow. Car stato four upon a C that is 400 upon 407 m per second. So time taken to cross the butch birth of the river crossing speed with this 400 So it will be 4.7 minute. So in this case, crossing the river time will be 4.7 Onda drifted speed will be beat a blue Pless be boat Sign up, Tito So down to the strip he will reach. See? We eat. I am marking it. He will reach at this point. Eat So be even Be on drifted speed and took time off crossing the river BW be butch Sign off theater and tow time off crossing the river Substituting the well 30 be both is 100. See the figures? It will be 75 of one 407 and took time off crossing the river 4.7 So it will be 1 97 m. So he will reach. They're both Bill. Reach down the stream on the north bank at a distance 1 97 m from the no deeper sorry. See part to reach at point C to reach at Wannsee at parting He must Sorry. At what angle must both must be revoked. Time off crossing the river distance travel and a speed of the boat by which it will reach reaching speed observed by Yeah, Just a moment, please. We have to calculator spirit off a boat with respect Toe observer on the other bank of the river that is north. Wink, let us here Suppose he is start from a This is the point B and this is see point A. B. You know, 400 m is he is sorry. B c is 75 m support. A vote is to be soon at Angle Theater. Then crossing speed will be the recalls. Off theater that is 100 cause off theater meter permanent. So time off crossing you can find it is to be switched off the river upon crossing speed that is 400 upon 100 question Onda drift velocity will be 30. Bless 400. Sign off theater So drift busy. It's called drip Felicity into crossing time Substitute This is given 75 m This is 30 plus 400 Sign off theater and toe 400 upon 100 Cause of theater. By solving this equation theater, you will get 83.5 degrees. I am up crossing the river 400 upon 100 costs off 83.5. So it is 4.2 seconds. Speed off the boat with respect to observer on the North Bank. So the speed off What speed output in this direction at Angle theater? Yeah, So a relative velocity off both with respect. Oh, observer is we go to square we flew off Water Square who looks course off 90 minus 83.5, substituting the value 100 30 chi square 100 30 course. So 6.5 on solving it, you will get it is to be 101 m per second. That's all. Thanks for watching it.