Answer:
She should make a rectangle with dimensions 14.4 cm by 4.2 cm.
Step-by-step explanation:
- The diagonal of a rectangle is represented by
. - Area of rectangle is = length×width
- Perimeter of a rectangle = 2(length+width).
Assume x be the width of the rectangle.
The length of the rectangle is to be 6 cm more than twice the width.
The length of the rectangle is= (2x+6) cm
Then the diagonal of the rectangle is 


cm
According to the problem,

Squaring both sides




⇒5x²+45x-21x-189=0
⇒5x(x+9)-21(x+9)=0
⇒(x+9)(5x-21)=0
⇒x+9=0 or, 5x-21=0

⇒x= -9, 4.2
Since the width of a rectangle can not negative.
So, x=4.2 cm
The width of rectangle is = 4.2 cm
The length of the rectangle is =(2×4.2+6)
=14.4 cm
She should make a rectangle with dimensions 14.4 cm by 4.2 cm.