30% of 15000 is 4500. This can be calculated by multiplying 30/100 by 15000, which gives (30*15000)/100 = 4500. Alternatively, we can use the following steps:

1. In the given case, the output value is 15000.
2. Let us consider the unknown value as x.
3. Consider the output value of 15000 = 100%.
4. In the same way, x = 30%.
5. On dividing the pair of simple equations, we get the equation as (15000%)/(x%) = 100/30.
6. Reciprocal of both the sides results in the following equation x%/15000% = 30/100.
7. Simplifying the above-obtained equation further will tell us what is 30% of 15000. We get x = 4500% .

Therefore, 30% of 15000 is 4500.