The maximum area is the area that uses half the fence (150 ft) for the side parallel to the barn and the other half for the ends of the pen (75 ft each). That area is 11,250 ft^2.
We have the function:

A turning point happens when the function reaches a maximum or a minimum.
In that points the value of the first derivative of the function is equal to 0.
So we can find the turning points by finding the first derivative and equal to zero:
Answer:
10/9
Step-by-step explanation:
Note that
- 12=2·2·<u>3</u>;
- 20=2·2·5;
- 36=2·2·<u>3</u>·3.
The common factors of these three numbers are 2, 2. Also numbers 12 and 36 have one more common factor <u>3</u>, then the least common multiple is
LCM(12,20,36)=2·2·<u>3</u>·5·3=180 sec=3 min (here first you write all common factors between all three numbers, then between two numbers and at last all remaining factors).
Answer: all three experiments will need to be checked after 3 minutes passed, then after 6 minutes passed, then after 9 minutes passed and so on.