Which instrument is used to measure atmospheric

What will come in place of the question mark (?) in the following series?

3.5, 9.5, 27.5, 81.5, 243.5, 729.5, ?

Choose the missing term.

R, U, X, A, D,?

70, 69, 73, 64,80, 55, ?

8       12       39       ?         180        216

120, 120, ?,  360, 900, 2700

Find the missing number in the given number series.

?, 26, 38, 70, 130, 226

33      41      25      49      17       ?

115% of 800 - 4/5 of 320 + 82% of 700 = ? – 102% of 500

60      61       57      66       ?       75       39