miles Posted January 4, 2012 Share Posted January 4, 2012 Anyone fancy having a go at this? Quote Link to comment Share on other sites More sharing options...
RobUK Posted January 4, 2012 Share Posted January 4, 2012 Are the given values the 12.5ft and the 3ft if the barrel? Quote Link to comment Share on other sites More sharing options...
miles Posted January 4, 2012 Author Share Posted January 4, 2012 Yeah sorry it's not too clears friend drew all over it trying to work it out. Quote Link to comment Share on other sites More sharing options...
Stephendjb Posted January 4, 2012 Share Posted January 4, 2012 12 ft Quote Link to comment Share on other sites More sharing options...
miles Posted January 4, 2012 Author Share Posted January 4, 2012 How did you work it out? Quote Link to comment Share on other sites More sharing options...
kjgreen3 Posted January 4, 2012 Share Posted January 4, 2012 Think I may be missing some maths teaching from being able to complete this, S.O.C.A.H.T.O.A and pythagoras' theorem aren't enough. I think breaking it up into triangles is the right way of finding a solution though. Gonna go buy a 12.5' ladder and borrow a 3 foot barrel and get my tape measure out to solve this one.......... Quote Link to comment Share on other sites More sharing options...
SupraStar 3000 Posted January 4, 2012 Share Posted January 4, 2012 I've solved it! You need to turn your head clockwise by 90º or rotate the document from portrait to landscape. Quote Link to comment Share on other sites More sharing options...
Graham1984 Posted January 4, 2012 Share Posted January 4, 2012 I thought it was the angle I can make my erection with weights dangling on the end. Quote Link to comment Share on other sites More sharing options...
tbourner Posted January 4, 2012 Share Posted January 4, 2012 It doesn't look possible! My brain hurts. How do you find out how far down the ladder it touches the barrel? Quote Link to comment Share on other sites More sharing options...
SupraStar 3000 Posted January 4, 2012 Share Posted January 4, 2012 I thought it was the angle I can make my erection with weights dangling on the end. Quote Link to comment Share on other sites More sharing options...
Digsy Posted January 4, 2012 Share Posted January 4, 2012 Just spent an hour or so on this to no avail. I thought you might be able to determine the angle between the ladder and the wall from the chord length across the "kite" shape and the segment angle in the center of the circle. The angle between the ladder and the wall plus the segment angle must equal 90 degrees because the other two internal angles in the kite are both 90degrees and all four together must total 360degrees. Knowing the angle between the ladder and the wall would give you the length C from the law of sines because the ratio of the sine of the angle of the ladder to the wall to the length C is equal to the ratio of the sine of the angle between the wall and the floor to the length of the ladder, both of whch are known. I'm stuck at calculating the chord length or the segment angle because there are too many unknowns. I bet its something really obvious... Quote Link to comment Share on other sites More sharing options...
Stephendjb Posted January 5, 2012 Share Posted January 5, 2012 How did you work it out? Simple trigonometry & cheated a little as it's a maths problem & won't have long fractional answers. That & I couldn't be bothered doing it properly so took a short cut Quote Link to comment Share on other sites More sharing options...
creative Posted January 5, 2012 Share Posted January 5, 2012 Simple trigonometry You guessed then? Show us your workings young man! Quote Link to comment Share on other sites More sharing options...
Rob Posted January 5, 2012 Share Posted January 5, 2012 Just spent an hour or so on this to no avail. I thought you might be able to determine the angle between the ladder and the wall from the chord length across the "kite" shape and the segment angle in the center of the circle. The angle between the ladder and the wall plus the segment angle must equal 90 degrees because the other two internal angles in the kite are both 90degrees and all four together must total 360degrees. Knowing the angle between the ladder and the wall would give you the length C from the law of sines because the ratio of the sine of the angle of the ladder to the wall to the length C is equal to the ratio of the sine of the angle between the wall and the floor to the length of the ladder, both of whch are known. I'm stuck at calculating the chord length or the segment angle because there are too many unknowns. I bet its something really obvious... I've forgotten so much of the maths I learnt, its criminal. I remember there was a way of working out the chord length using Cosines but I can't remember it at all. Quote Link to comment Share on other sites More sharing options...
mellonman Posted January 5, 2012 Share Posted January 5, 2012 I've forgotten so much of the maths I learnt, its criminal. I remember there was a way of working out the chord length using Cosines but I can't remember it at all. agreed funny how you remember things you use in life and not much about the rest, when i was 15 this would be easy but now? as said its all about working out the kite to give you the correct floor too ladder length Quote Link to comment Share on other sites More sharing options...
Stephendjb Posted January 5, 2012 Share Posted January 5, 2012 You guessed then? Show us your workings young man! How very dare you A right angle triangles sides can be worked out using x squared + y squared = z squared I looked at the value for z squared & applied a little logic. Question doesn't ask for working out or it would have taken longer to prove it. Quote Link to comment Share on other sites More sharing options...
tbourner Posted January 5, 2012 Share Posted January 5, 2012 How very dare you A right angle triangles sides can be worked out using x squared + y squared = z squared I looked at the value for z squared & applied a little logic. Question doesn't ask for working out or it would have taken longer to prove it. But you don't know y squared or x squared, you can't use that equation with only 1 known length! Quote Link to comment Share on other sites More sharing options...
Stephendjb Posted January 5, 2012 Share Posted January 5, 2012 It's a maths question not a real life situation the answer won't be to more than 1 decimal place and a 12 & a half foot ladder is a strange value to choose unless its to create a whole number answer.... The correct way of doing it is long and drawn out, my way took about 2 seconds feel free to prove my answer wrong. I can assure you it won't be. Quote Link to comment Share on other sites More sharing options...
Tyson Posted January 5, 2012 Share Posted January 5, 2012 It's a maths question not a real life situation the answer won't be to more than 1 decimal place and a 12 & a half foot ladder is a strange value to choose unless its to create a whole number answer.... The correct way of doing it is long and drawn out, my way took about 2 seconds feel free to prove my answer wrong. I can assure you it won't be. you are right it is root 145 which is roughly 12.0415945788. Quickest way to prove is to make an Iscoceles triangle to work out how high the ladder is off the floor (roughly 3.35) then its just pythagoras theorem. Quote Link to comment Share on other sites More sharing options...
Digsy Posted January 5, 2012 Share Posted January 5, 2012 It's a maths question not a real life situation the answer won't be to more than 1 decimal place and a 12 & a half foot ladder is a strange value to choose unless its to create a whole number answer.... The correct way of doing it is long and drawn out, my way took about 2 seconds feel free to prove my answer wrong. I can assure you it won't be. Yes, you are correct (I just constructed it on CAD to check). However, your method for working it out isn't a method at all. You have just looked at the figures and tried to fit the most sensible estimate of the result into the answer based on the assumption that the answer will be a whole number, which says more about yoru knowledge of how exam questions are written than your knowledge of maths. As you said, its a maths question, not a real world question - but your answer uses a real world solution rather than a mathematical one. If you really want to impress, then give us the answer to this one. Its exactly the same question but with user-unfriendly numbers. Quote Link to comment Share on other sites More sharing options...
Tyson Posted January 5, 2012 Share Posted January 5, 2012 Yes, you are correct (I just constructed it on CAD to check). However, your method for working it out isn't a method at all. You have just looked at the figures and tried to fit the most sensible estimate of the result into the answer based on the assumption that the answer will be a whole number, which says more about yoru knowledge of how exam questions are written than your knowledge of maths. As you said, its a maths question, not a real world question - but your answer uses a real world solution rather than a mathematical one. If you really want to impress, then give us the answer to this one. Its exactly the same question but with user-unfriendly numbers. 8.796448147 Quote Link to comment Share on other sites More sharing options...
tbourner Posted January 5, 2012 Share Posted January 5, 2012 So does anyone know the math answer for this then? I tried getting 2 triangles from the centre of the circle - so from centre of circle to ladder, which I believe would be a right angle, the ladder forms 2 adjacent triangle edges to the floor (triangle 1) and the wall (triangle 2), the centre of the circle then joins those points to make the triangles. We don't know what percentage of the 12.5ft forms the adjacent edges of each triangle, but I thought splitting it theoretically in half giving 6.25ft, means the 2 hypotenuse edges of each triangle must add up to root[1.5sqr+6.25sqr], so that means from the ladder/floor to the ladder/wall via the centre of circle must add up to 12.85496 (root[165.25]). I was planning on making another 2 triangles somewhere and doing some clever quadratic function comparison thing, but got bored. Quote Link to comment Share on other sites More sharing options...
Tyson Posted January 5, 2012 Share Posted January 5, 2012 So does anyone know the math answer for this then? I tried getting 2 triangles from the centre of the circle - so from centre of circle to ladder, which I believe would be a right angle, the ladder forms 2 adjacent triangle edges to the floor (triangle 1) and the wall (triangle 2), the centre of the circle then joins those points to make the triangles. We don't know what percentage of the 12.5ft forms the adjacent edges of each triangle, but I thought splitting it theoretically in half giving 6.25ft, means the 2 hypotenuse edges of each triangle must add up to root[1.5sqr+6.25sqr], so that means from the centre of circle to ladder/floor and ladder/wall must add up to 12.85496 (root[165.25]). I was planning on making another 2 triangles somewhere and doing some clever quadratic function comparison thing, but got bored. You only need two triangle, one right agled to work out the length of the isosceles triangle which is the height of the ladder then apply Pythagoras theorem to find out the length of the base Quote Link to comment Share on other sites More sharing options...
tbourner Posted January 5, 2012 Share Posted January 5, 2012 You only need two triangle, one right agled to work out the length of the isosceles triangle which is the height of the ladder then apply Pythagoras theorem to find out the length of the base But you never have enough sides of any isosceles triangles to work out the remaining side? Quote Link to comment Share on other sites More sharing options...
Tyson Posted January 5, 2012 Share Posted January 5, 2012 But you never have enough sides of any isosceles triangles to work out the remaining side? Use right angled traingle (red) to work out one side of the isosceles triangle (green) which then gives you the height of the main triangle (as two sides of the triangle are the same length) which you use pythagoras on. (3^2)+(1.5^2)= ~3.35 (12.5^2)-(3.35^2)= 145 which is ~12.04 squared Quote Link to comment Share on other sites More sharing options...
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