Which number produces a rational number when multiplied by 1/2

Which of the following is the missing term, a2, of the geometric sequence in which a1=2 and a3=200

Benito is selecting samples of five values from the table, which row will result in the greatest mean? population data row 1 4 2 2 3 3 row 2 3 3 4 3 2 row 3 2 4 3 4 3 row 4 3 4 4 7 3 row 1 row 2 r

How do you solve a question like this?