Problem, solve, thank you, solve problem, thank you

1. (noip10) 75 children went to the playground to play. They can ride a merry-go-round, ride a taxiway, ride a spaceship. 20 of them are known to have played all three, and 55 have played at least two of them.

If the cost of one ride is $5 for each ride, and the total income of the playground is $700, it is clear that there is a child who has not played any of them.

Just 55-20=35 people who have played two of them.

Just play one of the people cost 700-20 * (5 * 3) -35 * (5 * 2) = 50 yuan.

Just one of the hungry 50 5 = 10 people.

The number of people who have not played any of them 75-20-35-10 = 10 people.

2. A school football team has 30 jerseys, a basketball team has 15 jerseys, a volleyball team has 18 jerseys, and the total number of players in the three teams is 50, of which 2 people participate in 3 teams at the same time, so how many players only participate in two teams at the same time?

The principle of repulsion in the fifth grade.

a+b+c-(a and b coincide - a and c coincide - b and c coincide) + a, b, c coincidence = total.

30 + 15 + 18 - (a coincides with b - a coincides with c - b coincides with c) + 2 = 50

A coincides with B - A coincides with C - B coincides with C) = 30 + 15 + 18 + 2 - 50 = 15 people.

3. How many fractions are there in the simplest fraction with a denominator of 1001?

The molecule cannot contain a prime factor

That is, how many numbers from 1 to 1001 are not divisible?

1001 [7,11]=13, [7,11]--the least common multiple of 7 and 11.

143 + 91 + 77 - (13 + 11 + 7) + 1 = 281.

The number not divisible by 7, 11, 13 is 1001-281=720.

This situation encountered by the landlord should be caused by the system settings of the tablet electric Hu Sui brain,It is recommended that the landlord can back up the data and then restore the factory settings of the pants collapse computer,If it is still the same situation, you can directly contact the manufacturer's after-sales service to help upgrade the system,If there is no hardware problem, you can return to normal。

fox dead head hill] hú sǐ shǒu qiū].

Explanation]: Shouqiu: The mound where the head is facing the fox's den. Legend has it that when the fox will send his grandson to die, his head will be facing the hill where he was born. The parable does not forget the original. It is also a metaphor for missing hometown in the twilight years.

From]: Warring States Chu Qu Yuan "Nine Chapters Shijiang": "The bird flies against his hometown, and the fox will change his envy and loss when he dies." "The Book of Rites: Tan Gong Shang": "The fox died at the head of the hill, and benevolence was also." ”

Example]: I told you the story of "", a person who dies is nostalgic for the nuclear god's own homeland.

Grammar]: Linked; as a predicate; The metaphor is not forgetting one's roots or missing one's hometown.

If the total amount of cherry blossoms in the hall is 1, the unit price of A is 1 150, and the unit price of B is 1 90

This yields: x+y=100

x/150+y/90=1

Solve x=25

y = 75 dry bushes to buy 25 pieces of A and 75 pieces of B.

Hello. There are two known conditions for this question: (1) only R1; Simple (2) R1 and R2 are connected in parallel, with these two conditions, combined with Joule's law of heating, two equations are listed, and the relationship between E and R1 and R2 can be derived from these two equations.

2) R1 and R2 are stupidly missing. Similarly, using the Joule heating formula: (E 2 R1 + E 2 R2)*60s=80q, combined with the conclusion of (1), it can be seen that R2 E 2=30 Q

3) R1 and R2 in series. Set the time of power-on to t s. The Joule heating formula is also used to obtain:

t=3q。Sorting out this equation, moving the left to the right, and proposing t yields t=3q(r1 e 2+r2 e 2), and using the conclusions in (1) and (2), we can get t=120s

If you have any doubts, please ask, and look at it clearly. Thank you.

Lead tremor u2 r1*120=12j

u2/r1r2/(r1+r2)*60=8ju2/(r1+r2)*t=3j

Lian can immediately solve the problem of Huai Ant's defeat.

Each question is "the basic nature of scores".

1) 8 20 10 25 12 30 numerator and denominator expand by 2 times, 3 times, 4 times ...... at the same time（2）36/72 72/144

3) 8 12 4 6 2 3 From left to right, the numerator and denominator of each number are reduced by 2 times at the same time.

La-la.

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