A candidate who gest 20% marks in an examination, fails

A candidate who gest 20% marks in an examination, fails by 30 marks. But if he gets 32% marks, he gets 42 marks more than the minimum pass marks. Find the pass percentage of marks.

Let the full marks of exam be x.
According to the question,

=	x × 32	-	x × 20	= 30 + 42
	100		100

=	12x	= 72
	100

⇒ x =	72 × 100	= 600
	12

∴ Minimum marks to pass

⇒ x =	600 × 20	+ 30 = 120 + 30 = 150
	100

∴ Required percentage

=	150	× 100 = 25%
	600

Aliter : Using Rule 22,
Here, m = 20%, n = 32%, p = 30 and q = 42

Full Marks =	100	× (p + q)
	(n - m)

=	100	× (30 + 42)
	(32 - 20)

=	100 × 72	= 600
	12

∴ Passing Marks = 20% of 600 + 30

=	20 × 600	+ 30 = 120 + 30 = 150
	100

∴ Pass percentage =	150	× 100 = 25%
	600