The bag of candy n. Six of them orange. The rest - yellow. Hannah takes a piece of candy from a bag and eats. Then takes another one and again eats. The probability that she ate two orange candy - 1/3. Prove that n²-n-90 = 0.
blockquote> The strange story of Hannah gave birth to the completion of the network a lot of jokes. The most famous: "Hannah ate some chocolates. Calculate the circumference of the equator of Jupiter using tracing paper and a rusty spoon ».
Solution: Many netizens can not find a solution, because they are convinced that it is necessary to first calculate n, but in reality this is not required.
The probability that the first time Hanna pulled sweet orange - 6 / n (in a bag of six orange candy n). If the first time Hanna pulled sweet orange, then the probability of drawing the same second time - 5 / (n-1). Chance pull two orange candy - the product of these two probabilities.
We obtain: (6 / n) ⋅ (5 / (n-1)) = ¹/₃. Then enough to simplify the equation.
Where bus rides h2>
Mocking a simple task that falls to all the collections of this kind of puzzles - understandable for children and adults incomprehensible. Where bus rides?
Solution: are usually adults, seeing a diagram instantly forget about the details. In the US, children often go to school on the bus, so they know which side of his door, and he arrives. They realize that the picture is not enough doors. So, the bus goes to the left. Of course, an option that he rents ago, is not considered.
for patient h2> Yet another "viral" task. According to The Guardian, the Vietnamese teacher gives her an eight children, and they cope. In this solution in a short time we could not give even people with a doctorate degree in economics and mathematics.
It is necessary to fill the empty cells with numbers from 1 to 9 so that the expression was true.
Solution: with this puzzles, children are taught to memorize the order in which made the operations of addition, subtraction, multiplication and division. Unfortunately, in this case, the problem is not some kind of elegant and quick solution.
We must start by writing the table in the form of the equation:
a + (13⋅b / c) + d + 12⋅e - f - 11 + (g⋅h / i) - 10 = 66
Then bring it to mind:
a + d - f + (13⋅b / c) + 12⋅e + (g⋅h / i) = 87
It can be assumed that b / c and gh / i must be integers, and 13⋅b / c should not be too large. At this stage, many people prefer to write a program, but if you want you can just go through about a hundred options.
Children usually decide what to minimize 13⋅b / c, b should be equal to 2, and c - 1.
Get:
a + d - f + 12e + (gh / i) = 61
Then the children understand that they need to get rid of the 3, 5 and 7, causing difficulties in the division, and assign these values a, d and f, respectively.
Outcome: 12e + (gh / i) = 60
Play a little with the remaining numbers, you can find out what e = 4, g = 9, h = 8, i = 6.
Thus children solve this puzzle, if you always go the simplest way, and adults looking for a trick of life, it often can not cope.
via tjournal.ru/p/famous-tasks