Math (ugh) Homework Help

[ThatFatMan1911]

So I need some help with problem solving. I need to find the "aspect ratio" of the screen of my graphing calculator which measured, is 2 1/2" by 1 1/2" (W:H) I tried looking up some help on how to solve something like this but it's all done by, and for computer stuff and has nothing to do with the actual math behind it. 

 

Another example is finding the width and height of an older 25-inch tv whose screen has an aspect ratio of 4:3 "Find the area of this screen"

 

Can someone show me how to work problems like this? 

[shypin]

you divide the width by the height

 

 

calculator problem:

5/2

----  =  5:3   < thats the aspect ratio

3/2

 

 

25-inch tv problem:

 

the width:height is 4:3 so diagonal:width:length would be 5:4:3 (3-4-5 triangle, Pythagorean theorem)

if you plug in 25 then the width would be 20inch and height would be 15inch

multiply those two and you get the area 20*15=300in^2

[Godlygamer23]

Do you know the resolution of the display?

[linuxfan66]

So I need some help with problem solving. I need to find the "aspect ratio" of the screen of my graphing calculator which measured, is 2 1/2" by 1 1/2" (W:H) I tried looking up some help on how to solve something like this but it's all done by, and for computer stuff and has nothing to do with the actual math behind it. 

 

Another example is finding the width and height of an older 25-inch tv whose screen has an aspect ratio of 4:3 "Find the area of this screen"

 

Can someone show me how to work problems like this? 

its based on resolution and you calculate from there

 

for example 800/600 is your fraction.

so divide by 200

4/3.

so a ration of 4:3.

[itachipirate]

Do you know the resolution of the display?

He has the W:H dimensions, he doesn't actually need the resolution

This is an example of any ratio problem. You divide one given dimension by the other, and your answer will come out as a fraction. The fraction in this case is 3/5 (or 5/3 depending how you divide, it doesn't matter.) You take the numbers of the fraction (3 and 5) and put them in ratio notation (ex. 5:3.) The order is important, you can tell by the numbers they gave you which one goes where. The smaller number corresponds to the smaller side of the monitor, whereas the larger number corresponds to the larger side of the monitor. They gave you it in the order of W:H so that's how you should write it. The correct notation would be 5:3 (5 is bigger than 3, 2&1/2 is bigger than 1&1/2)

 

As for the second example I think you'd have to do some trigonometry/geometry to solve it. They give you 25inches, which I assume is the diagonal measurement of the monitor. And they give you 4:3 as a ratio for the sides. I don't remember my math very well so, I'm not sure how to solve from there. You'd break up the rectangle into two right triangles with a diagonal being the hypotenuse for both triangles with a length of 25. The answer to the second would be Length 20 and Width 15 (depending on how you look at the rectangle) because you have a ratio of 4:3, and you know the hypotenuse of the triangle has a length of 25. I cheesed it and looked up a Pythagorean triple with 25 for the hypotenuse, then checked to see if there were any triples containing two other numbers in a ratio of 4:3. Divide 4/3 and you get 1.334 and if you divide 20/15 you get 1.334. These two ratios are the same, 20 and 15 have a 4:3 ratio. 

 

You could've done this as well by multiplying each number in the 4:3 ratio by 2, then 3, (multiplication preserves the ratio) then so on and checking with the Pythagorean theorem (a^2+b^2=c^2) to see if the triangle could exist. You would've eventually multiplied both numbers of the ratio by 5 getting 20 and 15 for the sides, and knowing 25 as the hypotenuse you would've put this into the Pythagorean theorem and proved it correct

[SpaceNugget]

(2 1/2)/(1 1/2)

 

=

 

(5/2)/(3/2)

 

multiply by 2/2 ( 2/2 = 1 and you can always multiply by 1 )

 

cancel out the twos to leave 5/3

 

so the aspect ratio is 5:3

 

edit: ninja'd =(

[ThatFatMan1911]

Is there an easier way to find the width and height of a tv screen? I can't do any of that pythag stuff...

[linuxfan66]

Is there an easier way to find the width and height of a tv screen? I can't do any of that pythag stuff...

Look at the spec sheet?

[itachipirate]

Is there an easier way to find the width and height of a tv screen? I can't do any of that pythag stuff...

We're both 17, haven't you learned this stuff in school? That's just how to solve the whole theoretical problem with the information given. In any real-world scenario just look it up online, or measure it... I found a cool website for this online http://www.silisoftware.com/tools/screen.php?aspect_ratio=1.333&total_pixels=1764000 if you scroll to the bottom you can enter what you know, and get what you don't know. I entered 25 and aspect ratio of 4:3 and it spat out the rest

[ThatFatMan1911]

Look at the spec sheet?

Can't do that on a test?

[ThatFatMan1911]

We're both 17, haven't you learned this stuff in school? That's just how to solve the whole theoretical problem with the information given. In any real-world scenario just look it up online, or measure it...

No

[linuxfan66]

Can't do that on a test?

In a test all relevant information will be provided...

[ThatFatMan1911]

In a test all relevant information will be provided...

Sigh. Nevermind. 

[Glenwing]

Is there an easier way to find the width and height of a tv screen? I can't do any of that pythag stuff...

 

Not without a calculator. If you have one on hand, the most compact formula is this:

 

(this is for a 50" 16:9 screen, substitute whatever numbers you need)

 

50 x sin(arctan(16/9)) for the width, use cosine for the height (if in doubt, you can just do both and whichever one is larger is the larger side, etc.)).

 

Note that this will only give you the dimensions of the display panel itself though. It doesn't account for the size of the borders around the screen.

 

You should learn the Pythagorean theorem though, it's really basic and important. And useful

[SpaceNugget]

Is there an easier way to find the width and height of a tv screen? I can't do any of that pythag stuff...

you can use soh cah toa or you can use substitution