Find the least five digit number which leaves a remainder 9 in each ca...
Problem:
Find the least five digit number which leaves a remainder 9 in each case when divided by 12, 40, and 75.
Solution:
In order to find the least number that satisfies the given condition, we need to apply the Chinese Remainder Theorem.
Chinese Remainder Theorem:
The Chinese Remainder Theorem states that if we have a system of congruences:
x ≡ a₁(mod m₁)
x ≡ a₂(mod m₂)
...
x ≡ aₙ(mod mₙ)
where m₁, m₂, ..., mₙ are pairwise co-prime, then the system has a unique solution modulo M, where M = m₁m₂...mₙ.
Applying the Chinese Remainder Theorem:
We need to find the least five-digit number that leaves a remainder of 9 when divided by 12, 40, and 75. Let x be the required number. Then we can write:
x ≡ 9(mod 12)
x ≡ 9(mod 40)
x ≡ 9(mod 75)
We can see that 12, 40, and 75 are pairwise co-prime, so we can apply the Chinese Remainder Theorem to find the solution.
M = 12 * 40 * 75 = 36000
Now, we need to find the values of a₁, a₂, and a₃ such that the above congruences hold.
Finding the value of a₁:
We need to find the smallest multiple of 12 that leaves a remainder of 9. Let's start with 9 and keep adding 12 until we get a multiple of 12.
9, 21, 33, 45, 57, ...
57 is the smallest multiple of 12 that leaves a remainder of 9. So, a₁ = 57.
Finding the value of a₂:
We need to find the smallest multiple of 40 that leaves a remainder of 9. Let's start with 9 and keep adding 40 until we get a multiple of 40.
9, 49, 89, 129, ...
129 is the smallest multiple of 40 that leaves a remainder of 9. So, a₂ = 129.
Finding the value of a₃:
We need to find the smallest multiple of 75 that leaves a remainder of 9. Let's start with 9 and keep adding 75 until we get a multiple of 75.
9, 84, 159, ...
159 is the smallest multiple of 75 that leaves a remainder of 9. So, a₃ = 159.
Final Answer:
Now, we can substitute the values of a₁, a₂, and a₃ in the Chinese Remainder Theorem and get the unique solution modulo M.
x ≡ 57 * 250 * 159 + 129 * 225 * 159 + 9 * 112 * 40(mod 36000)