Final answer:
The length of the second pen is 39 cm.
Step-by-step explanation:
Chris measured one pen and it was 30 cm long. The second pen is 30% longer than the first pen.
To find the length of the second pen, we need to calculate 30% of the length of the first pen and add it to the original length.
Step 1: Calculate 30% of 30 cm = 0.30 x 30 cm = 9 cm
Step 2: Add the calculated value to the original length: 30 cm + 9 cm = 39 cm
Therefore, the length of the second pen is 39 cm.