Question 930808: What is the least number which is a multiple of 17 and when divided by2,3,4,5,6,8 leave as 1 reminder in each case
Answer by Edwin McCravy(20054) (Show Source):
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We are looking for 1 more than some multiple of 2,3,4,5,6,and 8.
We prime factor them all:
2 is prime
3 is prime
4 is 2x2
5 is prime
6 is 2x3
8 is 2x2x2
So their LCM must have 3 factors of 2, sice 8 does.
It must have 1 factor of 3
It must have 1 factor of 5
So the LCM of 2,3,4,5,6,8, 2x2x2x3x5 = 120
120 or any multiple of 120 will leave a remainder of 0
when divided by 2,3,4,5,6,8.
Therefore,
1 more than any multiple of 120 will leave a remainder of 1
when divided by 2,3,4,5,6, or 8.
We are seeking a number n which is 1 more than a multiple of 120 and
which is also a multiple of 17. Let the multiple of 120 than n is 1
more than be 120p and the multiple of 17 that n is be 17q. So for
our desired number n,
n = 120p+1 = 17q
Write 120 in terms of its nearest multiple of 17 which is 119,
because 119 = 7*17.
(119+1)p+1 = 17q
119p+p+1 = 17q
Divide every term by 17
Isolate the fraction terms:
The right side is an integer, so the left side is too.
Let that integer by A, then
So we multiply through by 17 to clear of fractions:
p+1 = 17A
So p = 17A-1
We want p to be as small as possible, so we take A = 1
and p = 17(1)-1 = 16
And since q-7p = A
q-7(16) = 1
q-112 = 1
q = 113
So:
n = 120p+1 = 17q
n = 120(16)+1 = 17(113)
n = 1920+1 = 1921
n = 1921 = 1921.
Answer: 1921
Edwin
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