Is there anyone who is good at math? Let s help the little brother

I also think it's 1 8

Because in the counting principle, this is a step-by-step count, which needs to be multiplied, assuming that the pencil is broken is an event, and the probability of the event that the first pencil is broken is 1 2, which is counted as the first step; The probability of the event that the second branch is broken is also 1 2, which is counted as the second step; The third branch is the same, it is counted as the third step, and the final result is 1 2*1 2*1 2=1 8

And so on, of course.

1.Do you understand that everyone has talked so much, and then I will tell you this, if it is a pen, according to the title it has two possibilities: broken and continuous, so the probability of breaking is 1 2;

2.If the two pencils are expressed as a and b respectively, then they have four cases: a and b are continuous, a is broken b continuously, a is constantly broken b is broken, and a is broken b is broken, so the possibility of both being broken is 1 4, that is, a has broken and continuous two cases, the probability of breaking is 1 2, b is also broken and the probability of breaking in the two cases is 1 2, these two are related to so it is 1 2 * 1 2 = 1 4;

3.If the 3 pencils are expressed as a, b, and c, then they have a, b, and c are continuous, a is broken b is continuous, a is broken b is constantly c, a is constantly b, c is continuous, a is constantly b is broken, a is constantly broken, a is broken c is broken, a is broken b is c, a is broken b is broken c is broken four situations, so the probability of all 3 is 1 8, that is, a has broken and continuous two cases, the probability of breaking is 1 2, b is also broken and continuous, the probability of the same break in both cases is 1 2, c is also broken and continuous, and the probability of the same break in both cases is 1 2, these 3 are related to so it is 1 2*1 2*1 2=(1 2) =1 8;By analogy, the chance of n pencils breaking when used one by one is (1 2).

I hope you understand and oh!!

The three pencils were used one by one, and the result was a 1 in 2 chance that they would all break

Use n pencils one by one, and the result is that the chance of all of them breaking is 1 in 2

That's how I understand it.

When using a pen, there are two possibilities of breaking and continuous, the probability of breaking is 1 2 When using two pens, there are 4 kinds of situations where two pens are broken, and the probability of breaking all is 1 2 * 1 2 = 1 4

And so on, the first question is 1 8, and the second question is (1 2) n

。。。One eighth of it... It will be one-half to the nth power.

1 8 Because once is 1 2, twice is 1 2*1 2, and three times is 1 2*1 2*1 2

n 1 2 multiplied.

500 pieces of paper yuan, every 100 pieces of Qi about potato Jingling Yuan (yuan 5 = yuan) manuscript liquid;

600 paper dollars, about yuan for every 100 sheets (yuan 6 = yuan);

800 paper dollars, about 8 yuan per 100 sheets.

800 paper dollars are cost-effective.

It's not cost-effective, you can go to 1688 to wholesale, and it's not only cheap, but it's also good, and you've been wandering around here for a long time.

Intelligence questions, IQ test. How many squares are there?

16 + 9 + 4 + 5 + 5 + 1 = 40 (pcs).

Quiz everyone: This is a math problem that can measure whether a person has business acumen. Master Wang is selling fish, a pound of fish at a price of 45 yuan, now a big sale at a loss, the customer bought a kilogram for 35 yuan, gave Master Wang 100 yuan fake money, Master Wang has no change, so he asked a neighbor for 100 yuan.

Afterwards, the neighbor found out that the money was fake in the process of depositing money, and it was confiscated by the bank, and Master Wang lost 100 yuan to the neighbor, how much did Master Wang lose in total?

Note: The difference between catties and kilograms.

A total loss of 100 + (45 2-35) = 100 + 55 = 155 yuan.

In mathematics, significant figures refer to the number in a number, from the first non-zero number of the number to the last number is called significant figures, such as there are three significant numbers, which are 6, 1, and 8.

A significant figure is a number that can actually be measured in the course of an analysis. What can be measured are uncertain numbers that include the last bit of the estimate.

Accurate numbers obtained by direct reading are called reliable numbers; The part of the number that can be estimated is called a doubtful number. All digits with one suspicious digit that reflect the size of the measurement result are called significant figures. The length of the object is measured as shown in the figure.

When data is recorded, the data bits that match the truth of the data we record and the experimental results are significant figures.

Hope it helps, significant numbers are from the first non-0 number on the left side of a number, to the last digit, all numbers are significant numbers of this number, that is, a number from the first non-zero number on the left to the end of the number, all numbers (including 0, scientific notation does not count 10 to the n power), called significant figures. To put it simply, remove all the 0s in front of a number, and everything from the first positive integer to the exact digit is a significant digit. Such as:

The first two zeros are not significant figures, and the following 109 are significant figures (note that the middle 0 is also counted).

A significant number is the first non-zero number counted from the left side of the number until the last number, and if two digits are retained, two digits are kept from left to right, and the rest are rounded.

Triangulation substitution derooting number, substitution x=asint, (0 to 2)1 (asint+acost)dasint= (0 to 2)cost (sint+cost)dt substitution u=( 2-t).

(2 to 0) sinu (cosu+sinu)d(2-u)= (0 to 2)sinu (sinu+cosu)du integral variable u directly to t

So definite integral = 1 2 1dt = 4

7/11 x = 21/44 dig.

x = 7/11 44 difference with 2/2 of a laugh and 11.

x=Do the math yourself!!

The most important thing for trigonometric functions is to exercise more from the morning, calculate more, and convert formulas into each other.

1, (from the causal method, it is observed that there is no function of a in the fruit, so I thought of eliminating the a function) sina + cosa = 2sinc

sinacosa=sin^2b...2

1 formula squared, 1 + 2 sinacos2 = 4 sin 2c ...3 At this point, it is not difficult to see that the common denominator between Type 2 and Type 3).

So: 2sin 2b = 4sin 2c-1

At this point, we are closer to the result, but the function name is different. At this point, it should be lowered) by the formula 2sin 2b = 1-cos2b (double angle formula: cos2b = cos 2b-sin 2b).

That is, 2-2cos 2c-1=1-cos2b can be simplified to obtain: 4cos 2

2c=cos^2b

2.The title is a bit unclear before reading. (But it proves that this kind of question needs to have the idea of "following the result", for example: you grasp the formula on the left, use the formula on the right as the standard, and turn the difference into the same.) ）

3.Ditto. 4.Problematic?

Keep the formula in mind!!