Answer:
- length: 24 inches
 - width: 18 inches
 
Explanation:
You want the length and width of a rectangle with a length : width ratio of 4 : 3 and an area of 432 in².
Similar figures
The rectangle of interest is similar to one with an area of (4 in)×(3 in) = 12 in². The area ratio is the square of the scale factor, so we have ...
 k² = (432 in²)/(12 in²) = 36 = 6²
 k = 6
The rectangle of interest has dimensions ...
 6 × 4 in : 6 × 3 in = 24 in : 18 in
The length and width are 24 inches and 18 inches, respectively.