Which type of operating system allows multiple users to

612, 487,?, 396, 388, 387

Find the missing number in the given number series.

1, 2, 6, 24, 120, ?

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

36, 85, ?,  230, 330, 451

Find the missing term in the series:

2, 5, 11, 23, 47, ?

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

400, 841, 1202, ?, 1716, 1885

44      45       41      50       ?       59       23

221, 100, 0, -81, ?

900     90      18      ?      2.16       1.08

16, 20, 11, 27, ?, 38

37, 57, 82, ?,  147, 187