Fencing a rectangular field that measures 37 ft by 27 ft How muchĩ7 is the largest prime less than 100. Give the place value for the indicated digit 8 in the number 138,350 Answer: Thousands 4. Who is correct?ġ.Write 4x4x4x4x4 as a power of 4. Greta said that the product of two prime numbers must also be a prime number. What is the first thing you should do to find the mean and range of data? a=put the numbers in order from least to greatest b=count the What function would you use to find the mean in a microsoft(R) excel document a=ROUND b=AVERAGE c=SUM d=HYPERLINK 2. A prime number can also be described as a counting number with exactly two factors, 1 and itself. Me, personally, I'm satisfied with two and a half seconds.How would you find all prime numbers that divide 50! (factorial)?Ĭan someone help me with prime and composite numbers? Prime numbers are counting numbers that can be divided evenly bt only two numbers:1 and themselves. Then I wrote a main() that notes the time before calling fillWithPrimes() with a quantity parameter of 1,000,000, and reports on the results: Eventually I came up with this: static int fillWithPrimes(int quantity) while (coPrimeFlag & currPrime <= squareRoot) My first draft took even longer than yours. Maybe this is one of those cases where you should avoid the use of objects in favor of an array of primitives. Five, ten seconds, that I'd find acceptable. Still, a minute and a half, while it would have been considered miraculous by Mersenne, is too slow today. If you're building up a list, you might as well use it to check potential primes.īenchmarking Java's a little difficult because you're at the mercy of the runtime system. If n is not divisible by 7, it won't be divisible by 49 either. If number is divisible then skipping the number else adding it to the prime listĭoes "2 till the square root of the number" include numbers like 4, 6 and 9? The only potential factors that need to be checked are numbers that have already been proven prime.
Adding 1 2 3 to the prime list initiallyĪctually, just 2 is sufficient.
It should be fairly easy to take the same approach in Java. This program can be altered to generate prime numbers on-demand as well.
Each time a new prime number is discovered, a filter is added to the stream so that the remainder of the stream gets filtered of any multiples of that prime number. N :: primes' (count' - 1) (filter s n) in Let rec primes' count' s = match count' with (* Get next prime, apply a new filter by that prime to the remainder of the stream *) (* Filter the given stream of any multiples of x *)
Here's an Ocaml program that implements the Trial division sieve (which is sort of the inverse of Eratosthenes as correctly pointed out by Will): (* Creates a function for streaming integers from x onward *)