A discount series of 10%, 20% and 40% is equal to a single discount of:_________?

A. 50%
B. 56.8%
C. 60%
D. 70.28%
Explanation:
Original price = Rs. 100
Price after first discount = Rs. 90
Price after second discount = Rs. (80/100 × 90) = Rs. 72
Price after third discount = Rs. (60/100 × 72) = Rs. 43.20
Single discount = (100 – 43.20) = 56.8%