Math Is Fun Forum

Slowlrnr

Member

Registered: 2010-01-26

Posts: 14

Need help with area of rectangle question

The length of a rectangular room is 6 feet longer than twice the width. The area is 80 sqaure feet. Find the length and the width of the room.

So L=2w+6

80=(2w+6)(w)

is this setup correct?  Somewhere in my calculations I am getting stuck.

80=2w^2 +6w
40-3w=w^2

I am getting messed up somewhere.

Can you assist?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Need help with area of rectangle question

Hi;

You are doing fine, can you solve the quadratic or do you need help?

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Slowlrnr

Member

Registered: 2010-01-26

Posts: 14

Re: Need help with area of rectangle question

I am stuck from there.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Need help with area of rectangle question

Hi;

You have the quadratic:

w^2 + 3w - 40 = 0

You need to factor it. Can you think of 2 numbers that when multiplied equal -40 and when added equal 3?

These pages will help you:

http://www.mathsisfun.com/algebra/facto … atics.html

http://www.purplemath.com/modules/factquad.htm

The factorization will be of the form:

( w +    ) ( w -    ) = 0

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Slowlrnr

Member

Registered: 2010-01-26

Posts: 14

Re: Need help with area of rectangle question

Hi;

You have the quadratic:

w^2 + 3w - 40 = 0

You need to factor it. Can you think of 2 numbers that when multiplied equal -40 and when added equal 3?

These pages will help you:

http://www.mathsisfun.com/algebra/facto … atics.html

http://www.purplemath.com/modules/factquad.htm

The factorization will be of the form:

( w +    ) ( w -    ) = 0

So you are saying W = 5
and the length = 16?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Need help with area of rectangle question

Hi;

That is very good and you are correct. Do you understand how to factor the equation to get the answer? This is important for future problems. I hope you didn't just go to some web page for the answer of that quadratic. That is fine to do when you know how but when learning you have to do it unaided.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.