What You Need: Find a volunteer to work your math magic on. Make sure your volunteer has some change in their pocket. But they do not reveal it to you.. Paper Pencil What To Do: Have your volunteer multiply their age by two. Then they will add five. Now multiply the previous sum by fifty. Subtract 365. Add the amount of pocket change, but do NOT count any change that is over *1. Add 115. Notice: that the first two digits will be the person's age,and the last two digits are the amount of the person's pocket change.