Hambone Posted August 26, 2006 Share Posted August 26, 2006 I am helping my daughter with her math homework. We can figure them all out except one. Since the folks on this forum are the smartest people on the face of the earth, I thought you might be able to assist. Here it is. If the height of a triangle with a base of 8 inches is tripled, it's area is increased by 96 square inches. Find the height of the triangle. I know that the area of a triangle is, 1/2 base x height. It just doesn't seem like there is enough information there to get the answer. Maybe I am just having a brain fart. Link to comment Share on other sites More sharing options...
JimBob2232 Posted August 26, 2006 Share Posted August 26, 2006 Final height = 36. Original height = 12 You can do it by trial and error if you wish, or you can do it the correct way. Set up these equations 1) A[o] = 1/2* b*h[o] 2) A[f] = A[o] + 96 3) A[f] = 1/2 * b * h[f] 4) h[f] = 3 * h[o] 5) Profit. Link to comment Share on other sites More sharing options...
Hambone Posted August 26, 2006 Author Share Posted August 26, 2006 Thanks for your help. Link to comment Share on other sites More sharing options...
crackur Posted August 26, 2006 Share Posted August 26, 2006 ack at math! Link to comment Share on other sites More sharing options...
Tolstoy Posted August 26, 2006 Share Posted August 26, 2006 I am helping my daughter with her math homework. We can figure them all out except one. Since the folks on this forum are the smartest people on the face of the earth, I thought you might be able to assist. Here it is. If the height of a triangle with a base of 8 inches is tripled, it's area is increased by 96 square inches. Find the height of the triangle. I know that the area of a triangle is, 1/2 base x height. It just doesn't seem like there is enough information there to get the answer. Maybe I am just having a brain fart. 752355[/snapback] My equation is slightly more crude than Jimbob's, but perhaps slightly more comprehensible: Let H=original height of the triangle 1/2(8H)=3[1/2(8H)]-96 4H=12H-96 H=3H-24 -2H=-24 H=12 Link to comment Share on other sites More sharing options...
Crap Throwing Monkey Posted August 26, 2006 Share Posted August 26, 2006 Or a little simpler, I think: you have two unknowns, the original height of the triangle (call it "h"), and the original area of the triangle ("a"). You know that half of the quantity base times height is the area, so a = (8*h)/2, and (a + 96) = (24*h)/2 ("24" coming from 8*3*h). Solve the first for "a" in terms of "h", which is just completing the division by two on the right hand side, so a = 4*h. Then substitute that into the second equation: 4*h + 96 = (24*h)/2 ...and solve (complete division by 2 on the RHS to get 4h + 96 = 12h, subtract 4h from each side to get 96 = 8h, divide by 8 and h = 12). That's nothing different from what anyone else did above me...but it might be clearer to some people the way I wrote it out. Link to comment Share on other sites More sharing options...
/dev/null Posted August 27, 2006 Share Posted August 27, 2006 well, since we're talking about he we solved the problem individually... We know...Triangle2 = Triangle1 + 96 We know...The formula for a triangle, bh/2 We know...The height of Triangle2 is 3 times Triangle1 We know...The base of Triangle1 = The Base of Triangle2 = 8 Therefore...we can take the formula of a triangle and conclude the area of Triangle1 is bh/2 Therefore...we can also take the formula of a triangle and conclude the area of Triangle2 is (b * 3h)/2 Giving us... (b * 3h) / 2 = bh/2 + 96 Get all of your unknowns on one side of the equation and all of your knowns on the other, so subtract bh/2 from both sides... (b * 3h) / 2 - bh/2 = 96 Plug in your known variable, b = 8... (8 * 3h) / 2 - 8h/2 = 96 Do some multiplying... 24h/2 - 8h/2 = 96 Bit of division... 12h - 4h = 96 Bit of subtraction... 8h = 96 And finally a bit more division.. h = 12 Link to comment Share on other sites More sharing options...
mcjeff215 Posted August 27, 2006 Share Posted August 27, 2006 There's got to be some way to work an integral into that. Makes math for kids so much more fun and entertaining. Link to comment Share on other sites More sharing options...
Dibs Posted August 27, 2006 Share Posted August 27, 2006 This is assuming a right angle triangle of course. Link to comment Share on other sites More sharing options...
Crap Throwing Monkey Posted August 27, 2006 Share Posted August 27, 2006 This is assuming a right angle triangle of course. 752839[/snapback] Doesn't matter. All triangles have an area of half the base times height. Link to comment Share on other sites More sharing options...
Dibs Posted August 27, 2006 Share Posted August 27, 2006 Doesn't matter. All triangles have an area of half the base times height. 753157[/snapback] Ooops....& you just know I mucked around then figuring out you are correct. ....& I used to be a math wizz. Link to comment Share on other sites More sharing options...
gmac17 Posted August 27, 2006 Share Posted August 27, 2006 Is your "son" named NJSue by any chance? Link to comment Share on other sites More sharing options...
mead107 Posted August 27, 2006 Share Posted August 27, 2006 for $10 i will tell you the answer . Link to comment Share on other sites More sharing options...
Mile High Posted August 28, 2006 Share Posted August 28, 2006 Is your "son" named NJSue by any chance? 753390[/snapback] Link to comment Share on other sites More sharing options...
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