After being marked down 20 percent, a calculator sells for Tk. The original selling price was-

A Tk. 20

B Tk. 12.5

C Tk. 12

D Tk. 9

Correct Answer: Option B

20% down means 80% of original price.

Thus,

80% of original price is 10 taka

100% of original price is = 10*100/80 taka

= 12.5 taka