If A denotes ‘–’, B denots ‘+’, C denotes ‘x’ and N denotes ‘÷’, then 15B9A15C10N5 = ?

Fill up the gap by finding out suitable answer:

9 : 49 : : 25: .... ?

Choose the correct alternative that will continue the series.

35, 57, 79, ...................

Length, breadth, height of a box are 4 cm, 12cm and 1m, if density of air is 1.2kg/m3 . The mass of air present in the box is:

100000 — 9899 =  .............?