Geometry homework - accuracy check

[Jessica]

Help me with these or check them. I may add more for you.


1. The perimeter and the ratio of the length to the width of a rectangle are given. Find the length and width of the rectangle.

P = 132 cm
l : w = 7 : 4

work/answer-

2(7x) + 2(4x) = 132
14x + 8x = 132
x=6

the length = 32
width = 24

2. The measures of the angles of a triangle are in the extended ratio given. Find the measures of the angles of the triangle.

3 : 4 : 10

work/answer-

20x = 180
x=9

measures: 27, 63, 90


Check these answers for now. I will/may have more later.

[Fazor]

Probably too late to help; but the answer to #2 is not in the correct ratio. Though, with the ratio you listed (3:4:10) the angles don't end up as whole numbers. I suspect the ratio is suppose to say 3:7:10, in which case your answer is right, or at least looks right to me.

[Zwarte Piet]

I don't think you're doing these right. For the first one, if the length and width are in a 7:4 ratio, then it can't be 32:24. That would be a 4:3 ratio.

[Fazor]

Originally Posted by Zwarte Piet

I don't think you're doing these right. For the first one, if the length and width are in a 7:4 ratio, then it can't be 32:24. That would be a 4:3 ratio.

Good catch; but she did it correctly, there's just an error in multiplication.


If x = 6, then 7x = 42, not 32.

[Zwarte Piet]

Another good catch^

Fazor is right about number 2. A 3:4:10 ratio cannot be correct because it would not be a triangle. One of the triangle rules is that the sum of any two sides must be greater than the third side. A 3:4:10 ratio would not pass this rule.

[Jessica]

my homework is not due until Monday. It's a packet.

[Fazor]

No me gustaba (?) tarea que era debida (?) en los lunes.

[Rusty]

Originally Posted by Fazor

No me gustaba (?) tarea que era debida (?) en los lunes.

No me gustaba la tarea que tenía que entregar los lunes.
No me gustaba la tarea que debe entregarse los lunes.

[Jessica]

huh? what does that mean?

I am aware of my mistakes. and yes, the ratio is supposed to be 3 : 7 : 10. I made a mistake while typing this :P same with the multiplication.

[Jessica]

Originally Posted by Fazor

No me gustaba (?) tarea que era debida (?) en los lunes.

Does that mean you don't like the homework to be due on Monday? Why not? It's pretty long.

[Fazor]

I *didnt* like it, no. It's been a while since I've had homework. I just hated having homework over the weekend.

[Jessica]

oh. well we got it on Tuesday last week, so yeah. I just finished it today. it was hard, but I finished it. most of them require pictures, though, so I won't be able to let you check them.

Here's another one:

The scale of a map and the distance between two points on the map is given. Find the actual distance between the locations represented by the points.

Scale: 4 in. : 1 mi.
Map distance: 10.5 inches

Is this right, what I did?

4 in/1 mi = 10.5 in/x mi

4x = 10.5
x = 2.625 mi

[Zwarte Piet]

Yes sir, that is correct!

[Fazor]

Actually, it's not.

X is the scalar (or whatever it's called).
You know that 4 inches is a (1) mile, so that's the fact you want to work with first.

It's 4X = 1, or x = .5 (miles).
Then it's a simple matter of multiplying the distance between two points (10.5) by X.

So, you approached the problem correctly, but you used the wrong number to find X.

[sosia]

I'm not a mathematician, but I don't see why is not OK what jchen did.
It's a "regla del tres"

[Fazor]

You're right. Her way works too. My mistake.
I would have done 4x = 1, therefore x = .25.
10.5 * .25 = 2.625.

So the answer is the same, just the method is diferent.

[Jessica]

I crossed multiplied then solved for x. That's what I did.

[Zwarte Piet]

Ya, that's probably the simpler method.