Question

An aquarium holding African cichlids is 4 inches higher than it is wide. Its length is 30 inches, and its volume is 4200 cubic inches. What is the length and width?

Answer 1

H = w + 4 ;
V = h × w × l ;
Then, 4200 = ( w + 4 ) × w × 30 ;
4200 ÷ 30 = ( w + 4 ) × w  ;
140 = ( w + 4 ) × w  ;
w^2 + 4w - 140 = 0 ;
 For ax^2 + bx + c = 0, the value of x is given by:    ;
In our case, a = 1 ; b = 4 ; c = - 140 
Roots are - 14 and 10 ;
The correct answer is w = 10inches because w > 0 ;
Finally, h = 14 inches .