Correct Option: B

(a) Single equivalent discount for 20% and 15%

=		20 + 15 −	20 × 15		% = 32%
			100

Single equivalent discount for 32% and 10%

=		32 + 10 −	32 × 10		% = 38.8%
			100

(b) Single equivalent discount for 25% and 12%

=		25 + 12 −	25 × 12		% = 34%
			100

Single equivalent discount for 34% and 8%

=		34 + 8 −	34 × 8		% = 42 – 2.72 = 39.28%
			100

Alternate method to solve this question :
Case I.
D₁ = 20%, D₂ = 15%, D₃ = 10%

Equivalent discount = 100 −

100 − D1

100 − D2

100 − D3

× 100

100

100

100

Equivalent discount = 100 −

100 − 20

100 − 15

100 − 10

× 100

100

100

100

Equivalent discount = 100 −		80	×	85	×	90	× 100
		100		100		100

Equivalent discount = 100 – 61.2 = 38.8%
Case II.
D₁ = 25%, D₂ = 12%, D₃ = 8%

Equivalent discount = 100 −

100 − D1

100 − D2

100 − D3

× 100

100

100

100

Equivalent discount = 100 −

100 − 25

100 − 12

100 − 8

× 100

100

100

100

Equivalent discount = 100 −		75	×	88	×	92	× 100
		100		100		100

Equivalent discount = 100 – 60.72 = 39.28%
⇒  Case II is better than Case I.