Percentage - Net Discount after series of discounts

Net Discount after series of discounts
Net Discount= (1- 1st discount%) X (1-2nd disscount %) and so on
E.g.
Discount on shirt 10% on 30%

Net discount = (1-0.1)(1-0.3)=(0.9*0.7)=0.63
or say 63 % net discount

Lets check this formula on shirt mrp 100 Rs.

After First Discount
=100-100*(10/100)
=100-10
=90

After Second Discount
=90-90*30/100
=90-27
=63

Percentage Change = Price After Discount / Original Price *100
=63/100*100
=63%