With Eduardo Kozuch's "Quick Addition," you will be able to perform just like a lightning calculator.
Removing three lists of numbers (from 100 to 1000) from your wallet and three envelopes, you invite three spectators to each select a number card and an envelope.
Because each envelope has two windows cut into it, each spectator selects two numbers on his chosen card, at random. Once the numbers are selected, the magician is instantly able to reveal the total of the six numbers that have been selected!
The numbers are different on all of the cards, and this works nothing like the old "Age Cards." It's a baffling mathematical masterpiece, and easy to do!