Chinese Remainder Theorem

Rarely Tested

Chinese Remainder Theorem: When a divisor can be split into two co-prime factors a and b such that N = a x b , then by dividing the given number M with individual factors such that remainder in each case is p and q that is M mod a = p and M mod b = q and two variables are introduced and an equation is formed such that ax+by = 1, it is important to note that x and y can only take integral values. So after finding the individual remainders of M when divided by factors a and b, this equation is solved to get integral values of x and y.

Thus, the Chinese remainder states that

M mod N = (aqx+ bpy) mod N

Where a and b are factors of divisors and are co-prime

p and q are individual remainders when M is divided by a and b

M mod a = p and M mod b = q

x and y are integers that satisfy the equation ax+by = 1

Question 1

Find the largest four digit number which leaves a remainder of 11 and 13 when divided by 13 and 15 respectively?

Question 2

Find the smallest four digit number which leaves a remainder of 4 and 6 when divided by 7 and 9 respectively?

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