How many parts per million (PPM) does 1.25% Carbon Dioxide equal?

To convert a percentage to parts per million (PPM), you multiply the percentage by 10,000. This conversion is based on the understanding that 1% is equivalent to 10,000 parts per million because 1% is 1 part per 100 parts, and when scaled to a million, it becomes 10,000 parts per million.

Here, if you take 1.25% and multiply it by 10,000, the calculation would be:

1.25% * 10,000 PPM = 12,500 PPM.

Thus, 1.25% of Carbon Dioxide corresponds to 12,500 PPM, making it the correct answer in this scenario.