9 problems make brainwaves worldwide brain pain

How many sentences can you solve without looking at the answer?

There are intuitive problems, just apply a common calculation to find the answer, but on the contrary, many problems pose tricky questions, causing many "brain pain" to be unable to think of sentences. reply. Here are 9 problems that have caused the online community to get up. How many sentences can you answer?

1. This 'brain hack' puzzle has two answers

In your opinion, what is the answer? The first solution is to add the result of the top row with the number of subordinates below, we will have the bottom row result (1 + 4 = 5, 5 + 2 + 5 = 12, .), so, we will The last number is 40.

However, there is still another solution: multiplying the second number in the calculation by the first number and then adding the first number (4 x 1 + 1 = 5, 5 x 2 + 2 = 12 .), if In this way, the final answer will be 96 .

2. The puzzle is simple but causes millions to argue

Results in 1 or 9?

If according to what we have learned in the school, the result will be 9, on the principle that the calculation in parentheses precedes 2 + 1 = 3. Then, if the series of calculations includes only subtraction and addition or permission multiplication and division must be performed from left to right. Thus, the order is 6: 2 x 3 = 3 x 3 = 9. This is the universal calculation method and is the most accurate result 'today'.

Controversy happens because some people use an old, popular rule before 1917, that is when using division calculation, it is understood that the divisor is all For example, x: 2y, if calculated by this rule, would be x: (2y), so the result of the above calculation would be 1 .

3. Simple puzzle, students answer correctly but the teacher says it is wrong to make the community indignant

Multiplication is commutative, which is probably well known. 5 x 3 is similar to 3 x 5. However, the teacher gives a wrong answer to the student's problem for the reason that . the program is not taught. When appearing on the Internet, this teacher's way of over-scoring machines made many people angry because of crushing the creativity and learning spirit of children.

4. The problem of guessing the birthday for grade 5 to adults also hurts the brain

This puzzle comes from Singapore and has drawn great attention to the online community. From the available data, you must guess the date of birth of Cheryl. If the information is correct and exclusion is applied, Cheryl's birthday will be July 16.

First, Cheryl only spoke separately to Albert and Bernard each person with information about the month and date of birth. Cheryl for 10 results to exclude. Try sorting them as the table below will be easier to eliminate.

Now let's see Albert and Bernard exchanging what they finally know Cheryl's birthday.

Albert: I don't know your birthday, but Bernard certainly doesn't know.

At the beginning, it was too clear, Albert only knew the month of birth because Cheryl had said it before, but the second one was an important clue. Why Albert knew Bernard did not know Cheryl's birthday, but after hearing Albert's reply, Benard knew:

'I don't know first, but now it's clear.'

If Cheryl told Bernard was 19 or 18, Bernard knew that it was May or June without waiting for Albert's sentence. Similarly, Albert states that Bernard did not know because the number of months that Cheryl disclosed to him is not 5 and 6.

Thus, we have removed half of the answers, the rest will be July 14, July 16, August 14, August 15 and August 17. We can continue to remove the 14th because there are two days overlapping.

Finally, we have three answers left, July 16, August 15 and August 17. Albert's final statement will be the key to solving the problem:

'Now I know Cheryl's birthday.'

For Albert to confirm so, Cheryl's birthday could only be in July because if it was August, there were still two possibilities.

Thus, Cheryl's birthday is 16/7 .

5. Questions for UK second-graders who thought it was hard but very easy

There were 19 people getting off at the first station. 17 others boarded the ship. The total time on board is 63 people. So, how many people are there on the ship at first?

It sounds like a headache, but you just need to write down the numbers that will be easy to imagine: 19 people who got out of the boat could understand -19, 17 more were +17.

-19 + 17 = -2, meaning that the ship lost two people at the beginning. The current number is 63, so the original number is 65 .

6. This question does not need to be good at math, just be observant

What is the car in the box?

This is not a problem, so do not waste effort to think of reasonable steps, just turn the image over and see that this is just the number range from 86 to 91 and the car is in box 87 .

7. Where is one dollar left?

This sentence is probably quite familiar. The lesson is as follows: 'I borrowed $ 50 from my mother and borrowed $ 50 from my father to buy a $ 97 bag. After buying, A left 3 dollars. A paid 1 dollar to his mother and 1 dollar to his father, holding 1 dollar. Now I owe $ 49 + $ 49 = $ 98, plus my $ 1 more is $ 99. Where is the remaining 1 dollar? '

In fact, no one is lost here, because you get confused. It is impossible to include 1 dollar left over the debt amount.

At first A's father had 50 dollars, A's mother had 50 dollars, A had 0 dollars

Final:

Dad A has 1 dollar + $ 49 but A debt ---> Dad A still has 50 dollars

A mother has 1 dollar + $ 49 but A debt ---> Mother A still has 50 dollars

A $ 1 + 1 bag (worth $ 97) + $ 98 debt ---> A has 1 + 97 - 98 = 0 dollars

So, at the beginning, each parent has $ 50, then each person still "has" $ 50

A $ 0 at the beginning has 0 dollars after all.

8. More than 50% of Harvard students, MIT, . answer this question wrongly

'The stick and the ball cost $ 1.10. The stick is $ 1 more expensive. So how much does the ball cost? '

More than 50% of respondents answered $ 0.1, meaning 10 cents. This is the wrong answer.

If the ball costs X dong and the stick is 1 USD more expensive, we have the stick price = X + 1

According to the lesson, we have ball + stick = X + (X + 1) = 1.10

2X + 1 = 1.10

2X = 0.1

X = 0.05 dollars = 5 cents

Behavior economist Daniel Kahneman explains why many people answer incorrectly:

"This puzzle brings up a visual answer, but it is wrong (10 cents). Try adding it up, you will see that if the ball costs 10 cents, the total price of the ball and club will be $ 1.20." .

 

Fill in the numbers 1 - 9 (do not duplicate) in the empty box on the solid image above.

This is not a trick at all, it is just a waste of time by filling in many times until you find the right number. The problem has 362,880 number filling capabilities, but only a few correct answers.

To simplify the problem, put it in the form of equations with a, b, c, d, e, f, g, h and i as numeric fill positions. We will have:

a + (13b / c) + d + 12e - f - 11 + (gh / i) - 10 = 66

Can be shortened to

a + (13b / c) + d + 12e - f + (gh / i) = 66 + 11 + 10 = 87

Or:

a + d - f + (13b / c) + 12e + (gh / i) = 87

From here, we can determine b / c and gh / i will be integers and 13b / c must not be too large.

There are many ways to fill out the correct answer, the Guardian page, with more than 100 correct ways to fill out. Here is one of those ways shared by a man named Brollachain:

For cluster 13b / c to be the smallest number, let b = 2 and c = 1. We will have:

a + d - f + 26 + 12e + (gh / i) = 87

Or:

a + d - f + 12e + (gh / i) = 61

Thus, we have left the numbers 3-9, where 3, 5 and 7 are prime numbers, you need to fill them in advance to avoid the equation confusion.

Let a = 3, d = 5 and f = 7.

Thus, we will have:

3 + 5 - 7 + 12e + (gh / i) = 61

Or:

12e + (gh / i) = 60

The remaining numbers are 4, 6, 8, 9.

Please replace it, you will get the most appropriate way of filling is e = 4, g = 9, h = 8, i = 6

48 + (72/6) = 48 +12 = 60