How to calculate the points on the following four playing cards to get 24? 10 9 3 1 How many ways can you think of?

The analysis is as follows:

When only addition, subtraction, multiplication and division are used, the simple reverse order method can be used in the primary operation, and one number can be deducted continuously until the calculation of two numbers is reversed.

A. (After deducting 10, can these two numbers be obtained from 9,3, 1),

-34, (can't) = = = = = = (whether we can get the four numbers of 43, 25, 34/9 and 34*9 from 3 1 after deducting 9, we can intuitively see that we can't, so we can't, so the following process is omitted).

14, (no)

Omit division, 2.4 (not allowed)

Multiplication abbreviation, 240 (not allowed)

B. (Can you get these two numbers from 1 0,3,1minus 9),

-33, (Yes, 33= 1 1*3,11=/kloc-0+1)

15, (no)

Omit division, (not allowed)

Abbreviation for multiplication, (not allowed)

C. (Can you get these four numbers after subtracting 3 from 9, 10 and 1),

-27, (No)

2 1, (not allowed)

8. (Not allowed)

72. (Not allowed)

D (after deducting 1, can these three numbers be obtained from 9, 3, 10),

-25, (not allowed)

23. (Not allowed)

24. (Not allowed)

Summary: When using four numbers (10,9,3, 1), only (10+1) * 3-9 =1* 3-9 = 30 can be used. That is to say, there is only one operation method for the 24-point simple operation of 10, 9, 3, 1 four numbers. ?

Extended data

Game steps

1, solved by 3×8=24 and 4×6=24.

Try to add the four numbers on the card face to 3 and 8, 4 and 6, and then multiply them. For example, 3,3,6 and 10 can form (10-6÷3)×3=24, etc. For example, 2, 3, 3, 7 can be in the form of (7+3-2 )×

2. Use the operational characteristics of 0, 1 1 to solve it.

For example, 3, 4, 4 and 8 can form 3×8+4-4=24. For example, 4,5, j and k can form11× (5-4)+13 = 24, etc.

3. In the deck with solutions, the following six solutions are widely used: (We use A, B, C and D to represent the four numbers on the deck)

①(a-b)×(c+d) such as (10-4)×(2+2)=24, etc. ②(a+b)÷c×d as (10+2)÷2×4=24, etc.

⑥(a-b)×c+d, such as (4-l)×6+6=24. Students may wish to try the above methods when playing games.

It should be noted that after accurate calculation by computer, among the four random integers of 1- 13 (the numbers can be repeated), the probability of being able to calculate 24 is about 74.835%.

"Clever calculation of 24 points" can greatly mobilize the coordinated activities of eyes, brain, hands, mouth and ears, which is very helpful to cultivate our rapid mental arithmetic ability and reaction ability.

Baidu Encyclopedia: 24 o'clock