When you remove the eggs that are in a basket 2,3,4,5,6 each time , remains 1,2,3,4,5 eggs respectively. When they are removed 7 by 7, don't remain any eggs in the basket. What is the small number of eggs that a basket in this conditions may contain?
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With N being the number of eggs in the basket, we have that
N ≡ ( k − 1 ) ( m o d k ) for each of k = 2 , 3 , 4 , 5 , 6 , and so
( N + 1 ) ≡ 0 ( m o d k ) for each of these values of k .
Thus N + 1 must be divisible by each of 2 , 3 , 4 , 5 and 6 . The least positive value that meets these conditions is LCM ( 2 , 3 , 4 , 5 , 6 ) = 6 0 , and thus the least possible value for N is 5 9 , and in general the possible values for N are of the form 5 9 + 6 0 m for any non-negative integer m .
Now we must deal with the condition that N is divisible by 7 . We thus need to find the least value of m such that 5 9 + 6 0 m is divisible by 7 . This is the case when
5 9 + 6 0 m ≡ 0 ( m o d 7 ) ⟹ 6 0 m ≡ − 5 9 ( m o d 7 ) ⟹ ( 5 6 m + 4 m ) ≡ 4 ( m o d 7 ) ⟹ 4 m ≡ 4 ( m o d 7 ) ,
the least positive solution for which is m = 1 .
Thus N = 5 9 + 6 0 ∗ 1 = 1 1 9 .