What is the smallest number that has 2,3 and 5 as factors?
Don't give me the answer though, just help me!
by 
ineedhelpfast
ANSWERS: 4
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multiples of five end in either a 0 or a 5. Multiples of 2 end in even numbers. Find a number that fits both of those and is divisible by 3. When I first read your question, I was a bit confused, but its actually really simple.
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Multiply all the numbers together. This will give you an answer that definitely has all three as factors. But work backwards from the highest number in the question just in case that's not the lowest one. Exampe find the smallest number that has 2,5 and 6 as factors: 2 x 5 x 6 = 60 Then work backwards in 6's from 60 just to be sure 54 , 48 , 36, 30, 24, 18, 12, 6 30 also fits all three numbers so it's the answer. Hope this helps!!
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This is called a "least common multiple". http://en.wikipedia.org/wiki/Least_common_multiple There is also the "greatest common divisor". Which is the biggest number to be the factor of all given numbers. http://en.wikipedia.org/wiki/Greatest_common_divisor . I suppose You can factorize numbers into a product of primes, e.g. 420 = 7 * 5 * 3 * 2 * 2 . So I'll show You the method for both LCM and GCD. . We have 3 example numbers (already factorized): A=2*2*2*3*3*3*3*5*5*5*5*5*5*7*7*7 B=2*2*3*3*3*3*3*5*5*5*5*5*7*7*7*7 C=3*5*5*5*5*5*5*5*5*7*7*7*7*7*7 . So LCM(A,B,C) is the number constructed of the largest amount of every prime number You can find in one of the numbers. I.e. The most 2s are in A. (There are 3) The most 3s are in B. (There are 5) etc. . So LCM will be: 2^3 * 3^5 * 5^8 * 7^6 ======================== GCD is the same, just You take the smallest amount of every prime number You can find. I.e. The least 2s are in C. (There are 0) The least 3s are in C. (There is 1) etc. . So GCD will be: 3 * 5^5 * 7^3 ========================= This method works for any (finite) amount of numbers.
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The way to figure out any smallest common multiple is to break down every factor to its elements and then use only each unique element once and multiply them. For instance the LCM of 3, 5, 15 and 20 must be 3 x 4 x 5. Although 4 can be broken up in 2 x 2, while it only appears in the 20, we must use the full 4.
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