Explanation:
If a is jointly proportional to the square of b and the cube of c, we can write:
a = k b^2 c^3
where k is some constant of proportionality. We can solve for k using the values given:
306 = k 8^2 7^3
306 = k 3,136
k = 306 / 3,136 ≈ 0.0974
Now we can use this value of k to find a when b=4 and c=5:
a = k 4^2 5^3
a = 0.0974 * 16 * 125
a ≈ 194.79
Therefore, when b=4 and c=5, a is approximately 194.79. Rounded to two decimal places, we get:
a ≈ 194.79