sorry for the question, and Yes I did buy the book's Thanks When I run the info I got 22 dpm/cm2 also just questioned the answer. now what would it me with a 2360 bkg 2 mins getting 2 cpm and 30 sec count time and I get 10 cpm A.

Here is your answer:

DPM = ( CPM - BKG ) / EFF

2360... I assume you mean the instrument is a Ludlum 2360 scaler/data logger. Again, that has nothing to do with the question. The probe is the only thing that matters... and that's only if you are trying to figure out for yourself what the probes efficiency is (which you are not). Compatible Detectors: 3-1-1, 43-2-2, 43-20, 43-68, 43-89 and 43-93. With the 43-89 being the most popular.

Again, it doesn't matter how long the background or sample count time is, if the result is already in CPM.

And lastly,

**you didn't tell me the efficiency.**DPM = ( CPM - BKG ) / EFF

DPM = ( 10 - 2 ) / EFF

DPM = ( 8 ) / EFF

If you were to use a generic 10% efficiency as an example, then the answer would be 8 / 10% = 80.

Please don't ask the same question a third time, that will tell me that you aren't trying to learn, you just want an answer. And I don't have time to do your work for you. I will help you learn, but you didn't appear to learn from the first question, because you asked the same basic question again.

Secondly, IF you did actual get a copy of the RCT Fundamentals, then I would suggest you spend more time with it.

Instead of asking for an answer, perhaps you could explain what part of the equation you don't understand, and we can help you with understanding the equation. OR... you can post what you think the answer is (showing your work), and ask if that is correct.

For these questions, the model number of the instrument is irrelevant. It is what is known as a 'distractor'. Just like the count time, if they have already given you the measurement in CPM.

If they say the instrument reads 10 total counts for a sample, and you counted the sample for 2 min, then that would be 10 counts per 2 min, or 10/2 = 5 counts per min, or 5 CPM.

Same thing with the background, it is just the CPM of the background. You subtract the CPM of the background from the CPM of the sample, to get your "Net CPM".

Once you calculate your Net CPM, you divide that by the efficiency to convert the CPM into DPM.