Final answer:
To find the length L when the volume V equals 210 ft³ and the width W is 5 ft, we first find the proportionality constant k from the given values, and then solve for L with the new volume and width.
Step-by-step explanation:
The volume V of a rectangular prism is directly proportional to its length L and width W. Given that V = 224 ft³ when L = 8 ft and W = 4 ft, we can find the constant of proportionality, k, using the formula V = k × L × W. Calculating k we get:
k = V / (L × W) = 224 / (8 × 4) = 7.
Now, when V = 210 ft³ and W = 5 ft, we can find the new length L using the original proportionality constant:
210 = 7 × L × 5L = 210 / (7 × 5)L = 6 ft
Therefore, the length L when the volume is 210 ft³ and width is 5 ft is 6 ft.