Tuesday

March 31, 2015

March 31, 2015

Posted by **aisha** on Wednesday, November 24, 2010 at 8:04am.

Write a simpified algebriac expression for the perimeter of a rectangle.

If the rectangle width is tripled and its length is doubled,the perimeter of new rectangle is 92cm greater than the original perimeter.

Find the area of the original rectangle.

- maths -
**Reiny**, Wednesday, November 24, 2010 at 8:34amoriginal width ---> x

original width ---> 5x-3

Perimeter = 2x +2(5x-3) = ....

new width --->3x

new length ---> 2(5x-3)

so 2(3x) + 2(5x-3) = 92

solve for x

....

then evaluate x(5x-3)

let me know what you get.

- maths -
**J**, Wednesday, November 24, 2010 at 8:34amHi aisha,

Let's start with formulating an algebriac expression for the perimeter.

We know that perimeter of rectangle = 2(length) + 2(width).

Since we don't know length or width, we let x be the width of the rectangle.

Hence length = 5x-3 [because length = (5 X width) - 3].

So perimeter = 2[5x-3]+2(x) = 10x-6+2x= 12x-6. That answers the first part.

If width is tripled, new width = 3x.

If length is doubled, new length = 2(5x-

3) = 10x-6. So new perimeter = 2(3x)+2(10x-6) = 6x+20x-12= 26x-12.

Now, perimeter of new rectangle - perimeter of original rectangle = 92cm.

So [26x-12]-[12x-6] = 92cm

Simplifying the left hand side, 14x-6=92cm

Therefore, 24x=98cm, x=98/14=7cm.

So to find area of original rectangle, it is length X width = (5x-3)(x) = 5x^2 - 3x = 5(7X7) - 3(7) = 224cm^2

Hope I helped! (:

-J

- maths -
**Reiny**, Wednesday, November 24, 2010 at 8:38amGo with J's solution, I noticed an error near the end of mine,

my equation should have been

2(3x) + 4(5x-3) = 92

- maths -
**J**, Wednesday, November 24, 2010 at 8:45amOops sorry! I realised that I also made a mistake near the end.

When I said "...Therefore, 24x=98cm.." I meant 14x (Not 24!) = 98cm. =)

- maths -
**rooi**, Wednesday, March 14, 2012 at 5:12amThe length of a rectangle is 3cm less than twice the width.The perimeter of the rectangles of the sides of the rectangle is 24cm.Find the lengths of the sides of the rectangle.

**Answer this Question**

**Related Questions**

basic geometric - 10. a rectangle has width the same as a side of a square whose...

Math - The variable W represents the width of a rectangle. The length of the ...

basic geometry - A rectangle has width the same asa a side of a square whose ...

geometry - If the length of a rectangle is twice its width, w, write an ...

math - the length of a rectangle is 5 ft more than twice the width. a)if x ...

algebra - The length of a rectangle is 5 inches longer than its width. Its ...

9th grade polynomials - How do you write the expression for the area of the ...

algebra , help - Can someone help me set up the equations thanks. Directions: ...

math117 - The area of a rectangle of length x is given by 3x2 +5x. Find the ...

math - The length, l, of a rectangle is 2 feet less than three times the width, ...