Question

the price p of an aluminum tube is jointly proportional to its radius r and the length l. if a 12-foot pipe with 5-inch radius costs 5250 pesos, how much will be the cost of a 9-foot pipe with a 6-inch radius?

Answer 1

4725 pesos

Explanation:

The price p of an aluminum tube is jointly proportional to its radius r and the length l.

For joint variation, we have the expression:

p ∝rl

Hence

p = krl

Step 1

Solving for k

if a 12-foot pipe with 5-inch radius costs 5250 pesos,

5250 = k × 12 × 5

5250 = 60k

k = 5250/60

k = 87.5

Step 2

how much will be the cost of a 9-foot pipe with a 6-inch radius

We make use of the expression:

p = krl

p = 87.5 × 9 × 6

p = 4725 pesos

Therefore, the cost is = 4725 pesos