Math Is Fun Forum

Toast

Real Member

Registered: 2006-10-08

Posts: 1,321

Some math comp. problems

[Problem uploaded as Jpeg]

I looked for similar triangles to try and solve this. I got:

So:

So the area of the circle would be:

This doesn't come up in the answers however, can someone correct me please.

Last edited by Toast (2007-02-23 22:45:58)

John E. Franklin

Member

Registered: 2005-08-29

Posts: 3,588

Re: Some math comp. problems

Draw the picture really big and you will see you need a 45 degree angle to center of circle.
On y = x line.
hypontenuse is y = -3x/4 + 3.
But since you have multiple choice, just do a rough estimate which should come to 2 or pi for the answer.
Then try pi, the correct answer, by assuming (1,1) is center
and then (1.6,1.8) is perpendicular with hypotenuse.
40% smaller triangle.

---

igloo myrtilles fourmis

John E. Franklin

Member

Registered: 2005-08-29

Posts: 3,588

Re: Some math comp. problems

Oh, the 40%, I forgot where I saw that, it is the height 3 minus 1, which is 2.
2 is 40% of 5 for the tiny triangle between (1.6,1.8) to (0,3) to (0,1.8).
So from (0,3) to (1.6,1.8) should be 2, yeah it is.
editting

Last edited by John E. Franklin (2007-02-24 10:19:02)

---

igloo myrtilles fourmis

Zhylliolom

Real Member

Registered: 2005-09-05

Posts: 412

Re: Some math comp. problems

BD is not the diameter of the circle! It is somewhat longer. This is your problem.

If you do the problem correctly you will get pi as your answer. Although technically none of those are correct, as it says "in centimeters" and area would be in square centimeters... owned.

George,Y

Member

Registered: 2006-03-12

Posts: 1,379

Re: Some math comp. problems

Last edited by George,Y (2007-02-24 14:52:40)

---

X'(y-Xβ)=0

Toast

Real Member

Registered: 2006-10-08

Posts: 1,321

Re: Some math comp. problems

Oh, and there's another one:

George,Y

Member

Registered: 2006-03-12

Posts: 1,379

Re: Some math comp. problems

A)3+Pi

Connect all origins. Connect origins to tangent points. You can get one equilateral triangle, and 3 rectangles.

Last edited by George,Y (2007-02-24 20:00:50)

---

X'(y-Xβ)=0

George,Y

Member

Registered: 2006-03-12

Posts: 1,379

Re: Some math comp. problems

For the first one.
5×r/2+4×r/2+3×r/2=S[sub]Δ[/sub]=3×4/2

find r

S[sub]o[/sub]=Pi×r²

---

X'(y-Xβ)=0

George,Y

Member

Registered: 2006-03-12

Posts: 1,379

Re: Some math comp. problems

S means area.

---

X'(y-Xβ)=0