题库列表

If the average (arithmetic mean) of 13, 17, x, 12 and 16 is greater than 15, which of the following must be true?

I. x is the median of the numbers

II. x is equal to 15

III. x is greater than the average of the numbers

Paleontologists in 1947 found a large group of fossilized skeletons of the carnivorous dinosaur Coelophysis. In the space where one Coelophysis's stomach had been, there were bones from another individual of the same species. The paleontologists concluded from this that Coelophysis was cannibalistic.

In order to evaluate the strength of the paleontologists’s argument, it would be most helpful to know which of the following?

The table lists 12-pack prices for Aquaphino Water sold in 39 US UDS Stores ("Up and Down the Street" stores) across 5 major cities on May 25, 2012. Store types are categorized as Grocers, Gas Stations, or C-Store (convenience store).

For each of the following statements, select Yes if the statement is true based solely on the information reported for the Accounts on this day. Otherwise, select No.

The average (arithmetic mean) of 5 distinct, single digit integers is 5. If two of the integers are discarded, the new average is 4. What is the greatest of these integers?

(1) Exactly 3 of the integers are consecutive primes.

(2) The least integer is 3.

 ­If the value of is positive, which of the following ranges represents the value of k?

Two containers contain milk and water solutions of volume x liters and y liters, respectively. What would be the minimum concentration of milk in either container so that when the entire contents of both containers are mixed, 30 liters of 80 percent milk solution is obtained?

(1) x = 2y

(2) x = y +10

Of the vehicles (cars and trucks) for sale at a certain dealership, 48 percent are cars that have 4 doors. If 80 percent of the cars for sale at the dealership have 4 doors, what percent of the vehicles are cars that do not have 4 doors?

In the 1980's, astronomer Bohdan Paczynski proposed a way of determining whether the enormous dark halo constituting the outermost part of the Milky Way galaxy is composed of MACHO's (massive compact halo objects), which are astronomical objects too dim to be visible. Paczynski reasoned that if MACHO's make up this halo, a MACHO would occasionally drift in front of a star in the Large Magellanic Cloud, a bright galaxy near the Milky Way. The gravity of a MACHO that had so drifted, astronomers agree, would cause the star's light rays, which would otherwise diverge, to bend together so that, as observed from Earth, the star would temporarily appear to brighten, a process known as microlensing. Because many individual stars are of intrinsically variable brightness, some astronomers have contended that the brightening of intrinsically variable stars can be mistaken for microlensing. However, whereas the different colors of light emitted by an intrinsically variable star are affected differently when the star brightens, all of a star's colors are equally affected by microlensing. Thus, if a MACHO magnifies a star's red light tenfold, it will do the same to the star's blue light and yellow light. Moreover, it is highly unlikely that a star in the Large Magellanic Cloud will undergo microlensing more than once, because the chance that a second MACHO would pass in front of exactly the same star is minuscule.

A factory has 80 workers and 3 machines. Each worker knows to operate at least 1 machine. If there are 65 workers who know to operate machine 1, 60 who know to operate machine 2 and 55 who know to operate machine 3, what is the minimum number of workers who know to operate all the three machines?

For any positive integer n, the sum of the first n positive integers equals . What is the sum of all the even integers between 99 and 301?