DNA analysis is the process in which genetic sequences are studied. It is used by law enforcement and medical personnel to identify a particular person or species, and even specific cancers and diseases. At one point the analysis process was very limited.
To round off to the nearest tenth, means to keep one decimal digit. (To round off to the nearest hundredth would mean to keep two digits; to the nearest thousandth, three; and so on. Now, the digit in the second decimal place is 5. Therefore add 1 to the previous digit 2.
You will notice that all three of the time signatures shown above have the bottom number of '4'. That tells us what kind of note gets the beat. In this case, the bottom number means a quarter note will get one beat. It is possible to have a number other than four on the bottom of a time signature, though. For example: an 8 on the bottom would tell us that an eighth note would get one beat. A 2 on the bottom would tell us that a half note would get one beat. There are many different combinations of numbers that can make up a time signature.