Welcome to ChineseRemainderTheorem.com!
Use the calculator below to get a step-by-step calculation of the Chinese Remainder Theory. Just enter the numbers you would like and press "Calculate" .
This removes all numbers from the textboxes, such that you can fill in your own.
This fills all textboxes with random numbers. If you fill in random numbers yourself, it is very likely that those numbers do not have a solution. To avoid disappointment, use this button instead! It only uses random numbers that do have a solution.
This button is similar to the "Clear everything" button, but only clears the left column.
This is useful if you want your equations to be of the form x ≡ a (mod m) rather than bx ≡ a (mod m).
In that case, it can be especially useful after using the random numbers button.
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Are you ready to view a full step-by-step Chinese Remainder Theorem calculation for the numbers you have entered? Then use this button!
Want to know more?- Read about how to execute the Chinese Remainder Theorem
- Discover different ways to calculate multiplicative inverses
Transform the equations
You used one or more of the fields on the left, so your equations are of the form bx ≡ a mod m.
We want them to be of the form x ≡ a mod m, so we need to move the values on the left to the right side of the equation.
For a more detailed explanation about how this works, see this part of our page about how to execute the Chinese Remainder algorithm.
First, we calculate the inverses of the leftmost value on each row:
| n | b | q | r | t1 | t2 | t3 |
|---|---|---|---|---|---|---|
| 41 | 243 | 0 | 41 | 0 | 1 | 0 |
| 243 | 41 | 5 | 38 | 1 | 0 | 1 |
| 41 | 38 | 1 | 3 | 0 | 1 | -1 |
| 38 | 3 | 12 | 2 | 1 | -1 | 13 |
| 3 | 2 | 1 | 1 | -1 | 13 | -14 |
| 2 | 1 | 2 | 0 | 13 | -14 | 41 |
Source: ExtendedEuclideanAlgorithm.com
| n | b | q | r | t1 | t2 | t3 |
|---|---|---|---|---|---|---|
| 189 | 25 | 7 | 14 | 0 | 1 | -7 |
| 25 | 14 | 1 | 11 | 1 | -7 | 8 |
| 14 | 11 | 1 | 3 | -7 | 8 | -15 |
| 11 | 3 | 3 | 2 | 8 | -15 | 53 |
| 3 | 2 | 1 | 1 | -15 | 53 | -68 |
| 2 | 1 | 2 | 0 | 53 | -68 | 189 |
Source: ExtendedEuclideanAlgorithm.com
| n | b | q | r | t1 | t2 | t3 |
|---|---|---|---|---|---|---|
| 661 | 301 | 2 | 59 | 0 | 1 | -2 |
| 301 | 59 | 5 | 6 | 1 | -2 | 11 |
| 59 | 6 | 9 | 5 | -2 | 11 | -101 |
| 6 | 5 | 1 | 1 | 11 | -101 | 112 |
| 5 | 1 | 5 | 0 | -101 | 112 | -661 |
Source: ExtendedEuclideanAlgorithm.com
Click on any row to reveal a more detailed calculation of each multiplicative inverse.
Now that we now the inverses, let's move the leftmost value on each row to the right of the equation:
x ≡ 139 × 243-1 (mod 41) ≡ 139 × 27 (mod 41) ≡ 22 (mod 41)x ≡ 565 × 25-1 (mod 189) ≡ 565 × 121 (mod 189) ≡ 136 (mod 189)x ≡ 381 × 301-1 (mod 661) ≡ 381 × 112 (mod 661) ≡ 368 (mod 661)
So now we have the following equations of the form x ≡ a (mod m):
x ≡ 22 (mod 41)
x ≡ 136 (mod 189)
x ≡ 368 (mod 661)
Now the actual calculation
- Find the common modulus M
M = m1 × m2 × ... × mk = 41 × 189 × 661 = 5122089 - We calculate the numbers M1 to M3
M1=M/m1=5122089/41=124929,M2=M/m2=5122089/189=27101,M3=M/m3=5122089/661=7749 - We now calculate the modular multiplicative inverses M1-1 to M3-1
Have a look at the page that explains how to calculate modular multiplicative inverse.
Using, for example, the Extended Euclidean Algorithm, we will find that:
So our multiplicative inverse is -20 mod 41 ≡ 21n b q r t1 t2 t3 41 124929 0 41 0 1 0 124929 41 3047 2 1 0 1 41 2 20 1 0 1 -20 2 1 2 0 1 -20 41
Source: ExtendedEuclideanAlgorithm.com
So our multiplicative inverse is 23 mod 189 ≡ 23n b q r t1 t2 t3 189 27101 0 189 0 1 0 27101 189 143 74 1 0 1 189 74 2 41 0 1 -2 74 41 1 33 1 -2 3 41 33 1 8 -2 3 -5 33 8 4 1 3 -5 23 8 1 8 0 -5 23 -189
Source: ExtendedEuclideanAlgorithm.com
So our multiplicative inverse is 242 mod 661 ≡ 242n b q r t1 t2 t3 661 7749 0 661 0 1 0 7749 661 11 478 1 0 1 661 478 1 183 0 1 -1 478 183 2 112 1 -1 3 183 112 1 71 -1 3 -4 112 71 1 41 3 -4 7 71 41 1 30 -4 7 -11 41 30 1 11 7 -11 18 30 11 2 8 -11 18 -47 11 8 1 3 18 -47 65 8 3 2 2 -47 65 -177 3 2 1 1 65 -177 242 2 1 2 0 -177 242 -661
Source: ExtendedEuclideanAlgorithm.com
- Now we can calculate x with the equation we saw earlier
x = (a1 × M1 × M1-1 + a2 × M2 × M2-1 + ... + ak × Mk × Mk-1) mod M
= (22 × 124929 × 21 +
136 × 27101 × 23 +
368 × 7749 × 242) mod 5122089
= 2805652 (mod 5122089)
So our answer is 2805652 (mod 5122089).
Verification
So we found that x ≡ 2805652
If this is correct, then the following statements (i.e. the original equations) are true:
243x (mod 41) ≡ 139 (mod 41)
25x (mod 189) ≡ 565 (mod 189)
301x (mod 661) ≡ 381 (mod 661)
Let's see whether that's indeed the case if we use x ≡ 2805652.