A kind of playing card is to randomly draw 4 cards and calculate 24 by addition, subtraction, multiplication and division. Let's see who's faster, what's the name of the game, and tell me the skills.

A kind of playing card is to randomly draw 4 cards and calculate 24 by addition, subtraction, multiplication and division. Let's see who's faster, what's the name of the game, and tell me the skills. Come on. Blackjack is a puzzle game played with playing cards. The content of the game is: draw 52 cards from a deck of playing cards, randomly draw 4 cards, and calculate the number (A stands for 1) on the card face through addition, subtraction, multiplication and division and brackets to get 24. Each card must be used once, but it cannot be reused. Different versions treat J, Q and K differently. The common version is to remove J, Q, K, or treat it as10; In another version, j stands for 1 1, q stands for 12 and k stands for 13.

-Wikipedia

Personally, I generally divide digital solutions into two kinds, one is integer solution and the other is

Involving the solution of fractions. Generally speaking, the latter is considered very difficult. Like what?

A classic example is 1, 5,5,5, and its solution is 5 × (5? 1 ÷ 5) = 24; Another example is 3, 3, 8 and 8, and the answer is 8 ÷ (3-8 ÷ 3) = 24. Because the latter uses dichotomy, its solution is hard to think of.

-Wikipedia

In actual combat, it is generally difficult to think of a solution involving fractions, so my personal suggestion is to give up directly.

Unless the subject thinks about this problem with research thinking, it is difficult to appear in the usual game and think of this solution.

In fact, this game has certain requirements for the sensitivity of numbers and mathematics, and the subject can exercise from the speed of mental arithmetic. Second, there are different tendencies for the solution of blackjack.

Top-down: Start with goal 24 and explore the required numbers until you reach a conclusion. For example, if there is n in the number you draw, then if we use the remaining three numbers to get the number of 24/n, 24-n, or 24+n, it is easy to deduce the answer. Then we take 24/N, 24-N and 24+N as the next goal and repeat the previous thinking mode.

Bottom-up: Explore all available numbers from the existing numbers in your hand until you get 24. For example, we have two numbers, M and N. We can get the number m+n m-n n-m n*m, and then add new numbers to expand the range of numbers we can get until it contains 24.

You can also do the first few steps of the above two steps at the same time to see if you can connect the answers in your mind.

One of the tips is to abandon too many numbers and fractions in the above process (although these numbers may not necessarily lead to conclusions) to improve the operation speed.