systems of conguences

There are certain things whose number is unknown. If we count them by threes, we have two left over; by fives, we have three left over; and by sevens, two are left over. How many things are there?

10 points · 3 comments · view on lemmy.world

3 Comments

threelonmusketeers@sh.itjust.works · 5 pts · 2y (1 reply)

105n + 23, where n is an integer.

cqthca@reddthat.com · 4 pts · 2y

it is implied that n = 0; you have the complete answer.

To others: this is modular math, Chinese remainder theorem From Wikipedia, the free encyclopedia

Sunzi's original formulation: x ≡ 2 (mod 3) ≡ 3 (mod 5) ≡ 2 (mod 7) with the solution x = 23 + 105k, with k an integer

In mathematics, the Chinese remainder theorem states that if one knows the remainders of the Euclidean division of an integer n by several integers, then one can determine uniquely the remainder of the division of n by the product of these integers, under the condition that the divisors are pairwise coprime (no two divisors share a common factor other than 1).

For example, if we know that the remainder of n divided by 3 is 2, the remainder of n divided by 5 is 3, and the remainder of n divided by 7 is 2, then without knowing the value of n, we can determine that the remainder of n divided by 105 (the product of 3, 5, and 7) is 23. Importantly, this tells us that if n is a natural number less than 105, then 23 is the only possible value of n.

ns1@feddit.uk · 1 pts · 2y

23 fits!