(1st) write out the Division Lemma equation for each piece of information
We are looking for a multiple or 17 (call it N for now) where:
N = 5a + 4
N = 7b + 6
N = 11c + 10
Where a, b, and c are non negative integer quotients
Each divisor gives the same exact Negative Remainder = -1
The first term that will satisfy each statement (ignoring the multiple of 17 requirement) will be -1 less than the LCM of the 3 divisors
N = LCM(5 ; 7 ; 11)* k - 1
Where k = non negative integer
N = 385k - 1
(2nd) we are given that N must be a multiple of 17 such that:
N = 17m
Where m = non negative integer
And
17m = 385k - 1
(3rd) at this point, since the answer choices are favorable, we can check one answer from (A) or (B) or (C) and then adjust based on how far from the condition we are
And then one answer from (D) or (E) if none of the first 3 satisfy the conditions
Or, we can use a Units Digit Analysis too see which answer choice must work
Since the question asks for the least multiple of 17, start with the first 3 answer choices.
1st positive multiple of 17 ——— 1 * 17 = 17
2nd positive multiple of 17 ——- 2 * 17 = 34
And so on
We are looking for the least positive multiple of 17 given:
17m = 385k - 1
385k = 17m + 1
On the LHS of the equation, the factor 385 multiplied by any non negative integer k will yield a Units Digit of either 0 or 5
Therefore, the RHS must yield a Units Digit of 0 or 5
In other words ——-> 17m + 1 must yield a Units Digit of of 0 or 5
(A)315th positive multiple of 17
(17) (315) + 1 ————> units digit of 6
(B)316th positive multiple of 17
(17) (316) + 1 ———-> units digit of 3
(C) 317th positive multiple of 17
(17) (317) + 1 ———-> units digit of 0
(C) is a possible answer!
(d) 384th positive multiple of 17
(17) (384) + 1 ———> units digit of 9
(e) 385th positive multiple of 17
(17) (385) + 1 ———-> units digit of 6
The only possible answer that could work is (c) 317th positive multiple of 17 = 5, 389
Condition 1:
5,389 ———-> divided by 5, remainder = 4
Condition 2:
5,389 ———-> divided by 7
4,900 is divisible by 7 ———> (5,389 - 4900) = 489
490 is divisible by 7, and 483 is divisible by 7
Thus the excess 489 when divided by 7 will yield a remainder = 6
Condition 3:
5,389 ————-> divided by 11
Remainder will be given by —-> (9 + 3) - (8 + 5) divided by 11
(12) - (13) = -1
-1 negative remainder is equivalent to a positive remainder of 10
Proof that all 3 conditions are satisfied
Answer (C)
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