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 |
|---|---|---|---|---|---|---|
| 356 | 409 | 0 | 356 | 0 | 1 | 0 |
| 409 | 356 | 1 | 53 | 1 | 0 | 1 |
| 356 | 53 | 6 | 38 | 0 | 1 | -6 |
| 53 | 38 | 1 | 15 | 1 | -6 | 7 |
| 38 | 15 | 2 | 8 | -6 | 7 | -20 |
| 15 | 8 | 1 | 7 | 7 | -20 | 27 |
| 8 | 7 | 1 | 1 | -20 | 27 | -47 |
| 7 | 1 | 7 | 0 | 27 | -47 | 356 |
Source: ExtendedEuclideanAlgorithm.com
| n | b | q | r | t1 | t2 | t3 |
|---|---|---|---|---|---|---|
| 301 | 331 | 0 | 301 | 0 | 1 | 0 |
| 331 | 301 | 1 | 30 | 1 | 0 | 1 |
| 301 | 30 | 10 | 1 | 0 | 1 | -10 |
| 30 | 1 | 30 | 0 | 1 | -10 | 301 |
Source: ExtendedEuclideanAlgorithm.com
| n | b | q | r | t1 | t2 | t3 |
|---|---|---|---|---|---|---|
| 643 | 646 | 0 | 643 | 0 | 1 | 0 |
| 646 | 643 | 1 | 3 | 1 | 0 | 1 |
| 643 | 3 | 214 | 1 | 0 | 1 | -214 |
| 3 | 1 | 3 | 0 | 1 | -214 | 643 |
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 ≡ 120 × 409-1 (mod 356) ≡ 120 × 309 (mod 356) ≡ 56 (mod 356)x ≡ 919 × 331-1 (mod 301) ≡ 919 × 291 (mod 301) ≡ 141 (mod 301)x ≡ 8 × 646-1 (mod 643) ≡ 8 × 429 (mod 643) ≡ 217 (mod 643)
So now we have the following equations of the form x ≡ a (mod m):
x ≡ 56 (mod 356)
x ≡ 141 (mod 301)
x ≡ 217 (mod 643)
Now the actual calculation
- Find the common modulus M
M = m1 × m2 × ... × mk = 356 × 301 × 643 = 68901308 - We calculate the numbers M1 to M3
M1=M/m1=68901308/356=193543,M2=M/m2=68901308/301=228908,M3=M/m3=68901308/643=107156 - 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 -153 mod 356 ≡ 203n b q r t1 t2 t3 356 193543 0 356 0 1 0 193543 356 543 235 1 0 1 356 235 1 121 0 1 -1 235 121 1 114 1 -1 2 121 114 1 7 -1 2 -3 114 7 16 2 2 -3 50 7 2 3 1 -3 50 -153 2 1 2 0 50 -153 356
Source: ExtendedEuclideanAlgorithm.com
So our multiplicative inverse is 120 mod 301 ≡ 120n b q r t1 t2 t3 301 228908 0 301 0 1 0 228908 301 760 148 1 0 1 301 148 2 5 0 1 -2 148 5 29 3 1 -2 59 5 3 1 2 -2 59 -61 3 2 1 1 59 -61 120 2 1 2 0 -61 120 -301
Source: ExtendedEuclideanAlgorithm.com
So our multiplicative inverse is 20 mod 643 ≡ 20n b q r t1 t2 t3 643 107156 0 643 0 1 0 107156 643 166 418 1 0 1 643 418 1 225 0 1 -1 418 225 1 193 1 -1 2 225 193 1 32 -1 2 -3 193 32 6 1 2 -3 20 32 1 32 0 -3 20 -643
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
= (56 × 193543 × 203 +
141 × 228908 × 120 +
217 × 107156 × 20) mod 68901308
= 61654272 (mod 68901308)
So our answer is 61654272 (mod 68901308).
Verification
So we found that x ≡ 61654272
If this is correct, then the following statements (i.e. the original equations) are true:
409x (mod 356) ≡ 120 (mod 356)
331x (mod 301) ≡ 919 (mod 301)
646x (mod 643) ≡ 8 (mod 643)
Let's see whether that's indeed the case if we use x ≡ 61654272.