A varies as the square of B and inversly as C. When A is 6 B is 5 and C is 100.

Calculate A when B is 12 and C is 72.

A = kB^2/C

So, AC/B^2 = k and is constant.

So, you want A such that

72A/144 = 6*100/25

To solve this problem, we'll use the formula for the variation of A in terms of B and C:

A = k * (B^2) / C

where k is a constant of variation.

Given that A is 6 when B is 5 and C is 100, we can substitute these values into the formula to find k:

6 = k * (5^2) / 100

To solve for k, we can rearrange the equation:

k = (6 * 100) / (5^2)
k = 12

Now that we have the value of k, we can use it to find A when B is 12 and C is 72:

A = k * (B^2) / C
A = 12 * (12^2) / 72
A = 12 * 144 / 72
A = 2 * 144
A = 288

Therefore, when B is 12 and C is 72, A is equal to 288.