Using HP 10bII for Markups and Margins

Q1: Find the margin if cost is $15.00 and selling price is $22.00?

Keystrokes:
15 [CST]
22 [PRC]
[MAR]

A1: After pressing [MAR] it display 31.81, this is the margin.

Q2: If cost is $20.00 and markup is 33%, what is the selling price?

Keystrokes:
20 [CST]
33 [MU]
[PRC]

A2: After pressing [PRC], it calculates and display the selling price, which is 26.20.

This solution is also applicable to HP 10b Financial Calculator.