To solve this problem, we can use the formula for direct and inverse variation:
T = k(d^2/f)
where k is the constant of proportionality.
To find k, we can use the values given in the problem:
192 = k(8^2/4)
Simplifying this equation, we get:
192 = k(16)
k = 12
Now that we have k, we can use the formula to find t when d=10 and f=6:
T = 12(10^2/6)
T = 200
Therefore, when d=10 and f=6, the value of t is 200.