Math

QuestionFind the perimeter equation for a rectangle with perimeter 120 cm120 \mathrm{~cm} and solve for xx. Options: a. 2x+5+6x1=1202x+5+6x-1=120, b. 4(6x1)=1204(6x-1)=120, c. 2(6x1)+2(2x+5)=1202(6x-1)+2(2x+5)=120, d. (2x+5)(6x1)=120(2x+5)(6x-1)=120.

Studdy Solution

STEP 1

Assumptions1. The perimeter of the rectangle is120 cm. The equations provided represent the perimeter of the rectangle3. We need to find the value of xx that makes the perimeter120 cm

STEP 2

We know that the perimeter of a rectangle is given by the formula 2(length+width)2(length + width). We can use this to evaluate each equation.

STEP 3

Evaluate equation a.
2x+5+6x1=1202x +5 +6x -1 =120Combine like terms.
8x+=1208x + =120

STEP 4

Subtract4 from both sides of the equation.
8x=12048x =120 -48x=1168x =116

STEP 5

Divide both sides of the equation by8 to solve for xx.
x=1168x = \frac{116}{8}x=14.5x =14.5

STEP 6

Evaluate equation b.
4(6x1)=1204(6x -1) =120Expand the equation.
24x4=12024x -4 =120

STEP 7

Add4 to both sides of the equation.
24x=120+424x =120 +424x=12424x =124

STEP 8

Divide both sides of the equation by24 to solve for xx.
x=12424x = \frac{124}{24}x=5.17x =5.17

STEP 9

Evaluate equation c.
2(6x)+2(2x+5)=1202(6x -) +2(2x +5) =120Expand the equation.
12x2+4x+=12012x -2 +4x + =120Combine like terms.
16x+8=12016x +8 =120

STEP 10

Subtract8 from both sides of the equation.
16x=120816x =120 -816x=11216x =112

STEP 11

Divide both sides of the equation by16 to solve for xx.
x=11216x = \frac{112}{16}x=7x =7

STEP 12

Evaluate equation d.
(2x+5)(6x)=120(2x +5)(6x -) =120Expand the equation.
12x22x+30x5=12012x^{2} -2x +30x -5 =120Combine like terms.
12x2+28x5=12012x^{2} +28x -5 =120This is a quadratic equation and cannot be solved for xx using simple algebra.

STEP 13

From the above steps, we see that only equation c gives a positive integer value for xx when the perimeter is120 cm. Therefore, the correct equation is c.
2(6x)+2(2x+5)=1202(6x -) +2(2x +5) =120And the solution for xx is7.

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