What is the Purpose of Instrument Tintometer?

840, 2520, 630, 3150, ?,  3675

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


75, 219, 388, ?, 809, 1065

4, 4, 5, ? , 248, 1248

21, 37, 73, 137, ?, 381

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


2, 5, 10, 17, 26, ?, 50

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

63, 92, ?, 158, 195, 224

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

29, 42, ?, 95, 135, 184

81, 41, 42, 64.5, ?, 330

1290, 1225, 1175, ?, 1112, 1095, 1085

8, 15, 44, 175, 874, ?