If Brianne's yard is 6 times the size of Alex's yard and Brianne's yard is 30 yards long, then Alex's yard is 30/6 = 5 yards long.
If Alex's yard is half the size of Derrick's yard, then Derrick's yard is 5 * 2 = 10 yards long.
Therefore, Derrick's yard is 10 yards long.
#### 10
The answer is: 10
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
Derrick measures the length of his yard. The length of Alex's yard is half the size of Derrick's and the length of Brianne's yard is 6 times the size of Alex's. If Brianne's yard is 30 yards long, how long is Derrick's yard, in yards?

### Answer:
