When a friend calls out "Wait a second, I have a trick to show you," don't you always stop and wait? Tricks are hard to resist. No one is ever too old to enjoy them or too young either. In fact, many of the most successful tricks are really quite simple. They don't require special equipments or hours of practice. For example, you tell a friend "Pick a card", then you surprise him by telling him which card he picked. Here's how it is done. Take a pack of cards and secretly look at the bottom card. Put the cards facedown on a table, and ask your friend to pick a card. Then place the card at the bottom.  Has your friend picked the cards by taking part of the cards from the top and putting it at the bottom? Start turning the cards up one at a time. You can pretend to think hard about each card. Look for the bottom card at the beginning which you have remembered. The cards that come after it will be the one your friend picked. Also, a mind-reading trick is fun to do at a party. You leave the room, and while you are gone, a tea cup is placed upside down over a penny, nickel($0. 05), dime($0. 1)or quarter($0. 25). When you come back into the room, you can tell which coin the tea cup is hiding. To do this trick, you only need a helper, or partner. Before hand, you two work out some signals. If he looks up. it's a penny; if he looks right, a nickel. You see, they are all very easy. Why not have a try? You can know which coin the tea cup is hiding because  _  .
a helper tells you by doing some actions it's very easy to guess you can take a look at it when no one is looking at your helper can guess the right answer and tells you secretly