A single discount equivalent to discount series 20%, 20%

Single equivalent discount for 20% and 20%

=		20 + 20 −	20 × 20		% = 36%
			100

Single equivalent discount for 36% and 10%

=		36 + 10 −	36 × 10		% = 42.4%
			100

Alternate method to solve this question :

= 100 −

100 − D₁

100 − D₂

100 − D₃

× 100

100

= 100 −

100 − 20

100 − 10

× 100

100

= 100 −	80	×	80	×	90	× 100
	100		100		100

= 100 – 57.60 = 42.40