Question

a rectangle has a diagonal which is 4 times the width if the area is 15root2 what are width andperimeter of the rectangle

Answer 1

Let width be x 
Area: 15√2
Diagonal; 4x 

First, you need to find the length using pythagorean theorem. 
a=x
c=4x
b=?

Solve this in terms of x and you will find the solution to be; √15x²

Knowing this, plug the number back into the area formula to find the value of x, 

(x)(√15x²)=15√2
...
..
x⁴=30 

Length= √(15√(30))

Do the calculations just to be sure 

Hope I helped :)