Изменения вступают в силу с 2014 года |
Министр образования и социальной защиты детей Великобритании Элизабет Трасс (Elizabeth Truss)объявила, что английским школьникам будет запрещено пользоваться калькуляторами при сдаче государственных экзаменов по математике в 11 лет. Министерство также планирует ограничить использование этих приборов на занятиях в начальной школе. Изменения вступают в силу с 2014 года, сообщает BBC News.
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Метки: калькулятор |
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Test Preparations |
AP | ACT | ASVAB | CUNY | CLEP | GED | GMAT | GRE | LSAT | MCAT | NCLEX | NLN | NYBI | NYSTCE | NYC | PSAT | NMSQT | Regents | SAT | SSAT | ISEE | TOEFL | USMLE |
AP | ACT | ASVAB | CUNY | CLEP | GED | GMAT | GRE | LSAT | MCAT | NCLEX | NLN | NYBI | NYSTCE | NYC | PSAT | NMSQT | Regents | SAT | SSAT | ISEE | TOEFL | USMLE |
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Метки: Test Preparations |
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The Physics of Everything |
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Метки: The Physics of Everything |
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луч, который притягивает объект к источнику излучения |
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24.10.2012, 19:12:00
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Физики предложили новую, более совершенную по сравнению с предыдущими схему притягивающего луча - так в фантастике называют луч, который притягивает объект к источнику излучения (например, такого рода лучи были у Звезды Смерти в "Звездных войнах"). Статья ученых появилась в Physical Review Letters.
В новой схеме притягивающий луч создавался парой соосных лучей Бесселя. Эти лучи - суть решение уравнения Максвела, в котором поток энергии поля описывается квадратом функции Бесселя нулевого порядка. Они обладают рядом замечательных свойств - в частности, фотоны в таких лучах движутся под углом к направлению распространения самого луча.
В ноябре 2011 года сразу несколько групп ученых показало, что, подбирая параметры луча особым образом, можно добиться того, что облученное тело (в работе рассматривались микроскопические объекты) будет излучать больше света в направлении от источника, чем к источнику. Как следствие, оно (тело) будет притягиваться к источнику.
В рамках новой работы ученые показали, что настройка луча должна быть очень точной. Они подчеркивают, что обеспечить такую точность в реальном времени не представляется возможным. Поэтому исследователи предложили другую схему, в которой используется пара лучей, которые накладываются в районе тела-цели. В рамках работы ученые даже смогли продемонстрировать работу собственной идеи экспериментально.
Насколько подобный луч пригоден для работы с микрообъектами (продвинутый аналог оптического пинцета), ученые пока затрудняются ответить.
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SHSAT Math |
This is a demo for SHSAT Math but the questions are not necessarily suitable for you.
[1] What is the value of 2020200/20 ?
Please select your answer:
A) 1010100 B) 1110 C) 10101 D) 111 E) 101010
[2] When expressing 1/11 as a decimal, you get 0.0909090909090909..., what is the 24th place to the right of the decimal point?
Please select your answer:
A) 8 B) 2 C) 9 D) 4 E) 0
[3] The following sequence of numbers are placed in the table as shown. Note that each number in the sequence is an even number. If the pattern continues, in which column will the number 372 appear?
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VIII |
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2 |
4 |
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32 |
34 |
36 |
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40 |
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42 |
... |
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Please select your answer:
A) IV B) VII C) IX D) VI E) X
[4] Which of the following can NOT be the product of two consecutive odd numbers?
Please select your answer:
A) 260877 B) 682275 C) 12040899 D) 3599 E) 374543
[5] If X = 9/10 , Y = 10/11 and Z = 42/50 , which of the following is correct?
Please select your answer:
A) Z < X < Y B) Z < Y < X C) Y < Z < X D) X < Y < Z E) X < Z < Y
[6] Which of the following has the largest value?
Please select your answer:
A) √ 39 + √ 47 B) √ 42 + √ 44 C) √ 43 + √ 43 D) √ 43 + √ 43 E) √ 35 + √ 51
[7] P, Q, R,and S are on a number line with S not shown in the below graph. The length of RS is 4 times the length of PQ. What is a possible coordinate of point S?
Please select your answer:
A) 44 B) -42 C) 45 D) -41 E) -45
[8] The graph below shows the sales of various flavors in an ice cream shop. If 40 Coffee flavor ice creams were sold, what is the number of Chocolate flavor ice creams sold in the shop?
Please select your answer:
A) 45 B) 43 C) 44 D) 50 E) 46
[9] If each of the fractions 2/X , 3/X , and 4/X is in its lowest terms, which of the following could be a value for X?
Please select your answer:
A) 45 B) 30 C) 64 D) 31 E) 60
[10] P and Q are natural numbers and P + Q = 15. What is the largest possible value of 1/P + 1/Q ?
Please select your answer:
A) 1+1/13 B) 1+ 1/14 C) 1+ 1/12 D) 1+ 1/2 E) 15/56
[11] All the three sides of a triangle have integer lengths. If one of the sides is 20, what is the smallest possible perimeter of the triangle?
Please select your answer:
A) 41 B) 38 C) 40 D) 43 E) can not be determined
[12] If a@b means (a + b) /5 , then what will 25@(24@26) = ?
Please select your answer:
A) 4 B) 3 C) 7 D) 6 E) 9
[13] If √ x + 1 /√ x = 4, then the value of 1 + x2 /x is
Please select your answer:
A) 14 B) 10 C) 11 D) 13 E) 12
[14] .(8) - .000(1) = ?
Please select your answer:
A) .8887 B) .79997 C) .887 D) .0007 E) .88887
[15] ABCD is a rectangle. E, and F are at the same height. If the area of the rectangle ABCD is 54, what is the area sum of the shaded triangles?
Please select your answer:
A) 13.5 B) 11.5 C) 14.5 D) 10.5 E) can not be determined
[16] Two triangles ABC and BCD share a common side BC. Below are the angles in degrees.
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54 |
62 |
64 |
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Which of the following is the longest line segment? Note that the diagram might not be drawn to scale.
Please select your answer:
A) BD B) AB C) CD D) AC E) BC
[17] In the figure below, three vertices A, B, and C of a quadrilateral fall on the circle circumference and the fourth at the circle center O. The measure of angle BCO = 67° and BAO = 68°. What is the measure of angle ABC?
Please select your answer:
A) 145° B) 135° C) 140° D) 120° E) It cannot be determined from the information given.
[18] Nick sells candy bars at a tailgate party to raise money for his school sports club. The candy bars are sold at 3 for $2, and he brought them at 5 for $1. How many candy bars must be sold in order to raise $21?
Please select your answer:
A) 48 B) 44 C) 45 D) 40 E) 38
[19] ABCD is a rectangle and DEC is a triangle. If the degree measure of ADE : AED : BCE = 2 : 4 : 1, what is the degree measure of DEC? Note that the diagram might not be drawn to scale.
Please select your answer:
A) 50 B) 45 C) 30 D) 35 E) can not be determined
[20] A spinner shown in the diagram has 10 equal sections. The probability of the pointer falling into each section is the same (Assume the pointer will never fall on a line between two sections). What is the possibility that the product of the two numbers that occur in two tries is a prime?
Please select your answer:
A) 7 /100 B) 3 /10 C) 11 /100 D) 1 /10 E) 2 /25
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Метки: SHSAT Math SHSAT Math |
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Demo for contest for 8th grade |
This is a demo for contest for 8th grade but the questions are not necessarily suitable for you.
[1] 5 consecutive natural numbers have a product 30240. What is the middle number among them?
[2] There are 10 cards with numbers 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 on them. These 10 cards were put in a box. You are asked to randomly pick up two cards each time to form a two-digit number. How many different two-digit numbers can you form?
[3] There are a number of basketballs, volleyballs, soccer balls, footballs, and kick balls. There are 29 students and each student picks 3 different types of balls. At least how many students will pick the same type of balls as someone else?
[4] Mary walked at 40 yards per minute, Rene walked at 43 yards per minute, and Jay walked at 48 yards per minute. Mary and Rene walked towards place B from place A, and Jay walked towards place A from place B. All three started at the same time. Jay met Rene first, and 3 minutes later he met Mary. How far is the distance between place A and place B (in yards)?
[5] There are 60 students. They line up to do exercises with each row having the same number of students. But the number of rows and the number of columns are required to be greater than 1. How many ways could the students be lined up?
[6] John started out at an average speed of 80 meter/minute from place A to place B. At the same time, George started out from place B to place A. When they met, John still needed 5 more minutes to get to place B, and George was 160 meters from place A. What is George's speed in meter/minute?
[7] Niconia had 3 times as much money in her account as David had in his account. After Niconia withdrew $550 from her account, and David deposited $650 to his account, David's account has twice as much as what remained in Niconia's account. How much money did Niconia have before she withdrew the money?
[8] There is an apple tree in the back yard at Helen's house. On the 1st day, she picked 1/9 of all the apples in the tree; On the 2nd day, she picked 1/8 of all the apples remaining in the tree; On the 3rd day, she picked 1/7 of all the apples remaining in the tree; On the 4th day, she picked 1/6 of all the apples remaining in the tree; On the 5th day, she picked 1/5 of all the apples remaining in the tree; On the 6th day, she picked 1/4 of all the apples remaining in the tree; After 6 days, there are 135 apples left in the tree. How many apples were there in the tree to begin with on the 1st day?
[9] M + N + L = 6, and M, N, and L are natural numbers. How many different solutions are there for M, N, and L in the equation? Note M=1, N=2, L=1 and M=1, N=1, L=2 are different solutions for M + N + L = 4.
[10] From the natural numbers 1 to 91, pick any two numbers whose sum is less than 92. How many ways are there to pick?al numbers 1 to 81, pick any two numbers whose sum is less than 82. How many ways are there to pick?
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Метки: demo contest for 8th grade contest 8th grade Math |
Demo for contest for 7th grade |
This is a demo for contest for 7th grade but the questions are not necessarily suitable for you.
[1] Some roses are put into vases. If each vase holds 4 roses, 7 roses are left. If each vase holds 5 roses, 4 more roses are needed. How many roses are there?
[2] The students lined up in rows to do some exercises. If 27 students are in each row, 3 students are left; if 24 students are in each row, 3 students are left; if 30 students are in each row, there are still 3 students left. At least how many students are there?
[3] There are 10 cards with numbers 1, 1, 2, 3, 4, 5, 6, 7, 8, and 9 on them. These 10 cards were put in a box. You are asked to randomly pick up two cards each time to form a two-digit number. How many different two-digit numbers can you form?
[4] Find the sum of all digits in the first 88 natural numbers: 1, 2, 3, 4, ..., 86, 87, and 88.
[5] Ben walked at 45 meters per minute, Josh walked at 50 meters per minute, and Rene walked at 58 meters per minute. Ben and Josh started out from place B together, and Rene started out from place A (behind B) at the same time in same direction as Ben and Josh. Some time later, he caught up with Ben, and then 5 more minutes later, he caught up with Josh. Find the distance (in meters) between place A and place B.
[6] There are a total of 31 ducks and rabbits, with a total of 90 feet. How many ducks are there? . How many rabbits are there? .
[7] There are 6 cards with numbers 0, 3, 4, 5, 6, and 7 on them. These 6 cards were put in a box. You are asked to form a three-digit number by: a) Randomly pick up a card. If the card has number 0, then put it back and re-pick one until the number on the card is not zero. Write down the number as the 1st digit and put the card back in the box; b) Randomly pick up the 2nd card. Write down the number as the 2nd digit and put the card back in the box. c) Randomly pick up the 3rd card. Write down the number as the 3rd digit and put the card back in the box. If you keep doing this, how many different three-digit numbers can you form?
[8] The distance between place A and place B is 30 miles, and the two locations are connected by a hilly road. One part of the road is uphill, the remaining part is downhill. It took Nick 5.7 hours to bicycle from place A to place B. When he went back from place B to place A on the same road, it took him 4.3 hours. Assume that he kept one speed for uphill ride and another speed for downhill ride. If the speed for the uphill ride was 5 mph, what was the speed of the downhill ride(in mph)?
[9] A turtle and a rabbit were running a 3960 meter race. The speed of the rabbit was 15 times of the speed of the turtle. During the race, the rabbit stopped and took a nap. When he woke up, the turtle was ahead of him. He started to catch up with the turtle with the same speed as before. However when the turtle got the destination, the rabbit still had 900 meters more to go. How many meters did the turtle run during the time the rabbit was taking a nap?
[10] From the natural numbers 1 to 81, pick any two numbers whose sum is less than 82. How many ways are there to pick?
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Метки: demo contest for 7th grade contest 7th grade Math |
Demo for Math contest for 6th grade |
This is a demo for contest for 6th grade but the questions are not necessarily suitable for you.
[1] A shirt was charged $1.96 with a 4% sales tax rate included. What was the cost of the shirt(in dollars)before the tax was included?
[2] Niconia has 3 shirts, 5 pants, and 3 shoes. How many different ways can she dress up?
[3] John has 4 choices of roads from home to school. There are 5 choices of roads from school to library. How many choices of roads does John have if he gets to school from home, then goes to the library from school?
[4] Eric rode his bike to a baseball practice at 15 mph. On his way home, he only pedaled at 10 mph. What was his average speed (in mph) for the entire trip?
[5] Laura went shopping. She spent one-third of her money in the 1st store. She went to a second store where she spent one-fourth of what remained, and then had $102 left. How much money (in dollars) did she have before she went to the 1st store?
[6] There are 80 balls of 8 different colors in a bag. There are an equal number of balls for each color. At least how many balls need to be taken out from the bag so that there are 4 balls which are of the same color?
[7] If 12+22+32+ ...+272+282+292 = 8555, what is the value of 22+42+62+ ...+542+562+582 =?
[8] There are one $5 bill, four $2 bills, and eight $1 bills. If Ben needs $9, how many ways could he make up the money from those bills?
[9] Express the following sum as a simple fraction in lowest terms:
[10] A series of numbers '345678345678345678...' has a certain pattern. What is the sum of the first 84 digits in the number starting from the left side?
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Метки: Demo Math contest for 6th grade Math contest 6th grade Math contest |
Задачи Московской математической олимпиады |
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Метки: Задачи Московской математической олимпиады Задачи Московской математической олимпиады Московской олимпиады |
