Calculae - a card game involving basic arithmetic

The game has been refined after some playtesting, and this version should be quite playable and fun. It is also surprising brain-taxing. To play the game, you need to print 54 monochrome cards (card graphics at http://www.boardgamegeek.com/filepage/46696) , and get 1 or 2 decks of regular Poker decks. There is also a Solitaire version.

Introduction
Calculae is a card game involving basic arithmetic. Players use cards to form math expressions that evaluate to a desired result. It is an educational and fun game for people who want to improve and exercise their arithmetic skills.

Number of players
1 - 4

Game Components
- 54 Poker cards for 1-2 players, 108 Poker cards for 3-4 players
- 12 Operator cards (3 plus, 2 minus, 2 multiply, 1 divide, 1 pair of parenthesis, 1 square, 1 cube)
- 42 Result cards (Prime numbers up to 181)

Setup
Deal 5 Poker cards to each player. Place the rest of the Poker cards face-down in a Poker draw pile, the Operator cards face-up in the middle of the table, and the Result cards face-down in a Result draw pile.

Multi-player Game Play (2-4 players)
During the start of each round, put the top card from the Result draw pile on the table face-up in a Result discard pile. Each player then selects 2 or more Poker cards in his hand such that using these cards and at least 1 Operator card, he is able to form a math expression that evaluates to the number on the face-up Result card. Jokers can represent any number from 1 to 13.

All players put their selected Poker cards in front of them face-down. If a player thinks he is unable to form any correct math expression with his current hand, he has to place all his 5 Poker cards face-down. Once all players have done this, each player reveals his selected Poker cards and take turns to form the expressions with the Operator cards. If the player forms the expression correctly, then he places his Poker cards face-down in front of him in his Score pile.

For the player who is unable to form any expression and has placed his 5 Poker cards on the table, he will reveal his cards and other players have a chance to form an expression. Any of the other players may shout “Calculae!” and then start to form an expression. If the expression is formed correctly, he gets to keep the Poker cards used in his Score pile.

If a player makes an attempt to form an expression, either using his Poker cards or other player’s Poker cards, and is unable to do so or forms an incorrect expression, he will have to discard 3 cards from his Score pile to the Poker discard pile face-up.

Once all players have verified their expressions formed, they draw Poker hands to fill their hand to 5 and the next round starts where a new Result card is revealed. The new Result card is placed on top of the current Result card.

Continue playing until either the Poker draw pile or the Result draw pile runs out. The winner is the player with the highest Score.

Solitaire Game Play (1 player)
All the rules are the same, except that the player has to discard all his cards at the end of a round, whether he has formed an expression or not. Then he draws 5 new Poker cards for the next round. The aim is to score the highest Score.

I have thought about power and root. I figured mostly only powers up to 2 and 3 is needed, thus I have only included the square and the cube, and not the power operator. For root, it is seldom usable since you need a perfect square to use it. Absolute value, however, is something worth including in the next version. Thanks!