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.
Do you want to use more equations? Go ahead and use this button. It adds another row that you can fill in. Not sure what numbers to put in this newly added row? Use the random numbers button again!
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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 |
|---|---|---|---|---|---|---|
| 685 | 718 | 0 | 685 | 0 | 1 | 0 |
| 718 | 685 | 1 | 33 | 1 | 0 | 1 |
| 685 | 33 | 20 | 25 | 0 | 1 | -20 |
| 33 | 25 | 1 | 8 | 1 | -20 | 21 |
| 25 | 8 | 3 | 1 | -20 | 21 | -83 |
| 8 | 1 | 8 | 0 | 21 | -83 | 685 |
Source: ExtendedEuclideanAlgorithm.com
| n | b | q | r | t1 | t2 | t3 |
|---|---|---|---|---|---|---|
| 661 | 332 | 1 | 329 | 0 | 1 | -1 |
| 332 | 329 | 1 | 3 | 1 | -1 | 2 |
| 329 | 3 | 109 | 2 | -1 | 2 | -219 |
| 3 | 2 | 1 | 1 | 2 | -219 | 221 |
| 2 | 1 | 2 | 0 | -219 | 221 | -661 |
Source: ExtendedEuclideanAlgorithm.com
| n | b | q | r | t1 | t2 | t3 |
|---|---|---|---|---|---|---|
| 557 | 869 | 0 | 557 | 0 | 1 | 0 |
| 869 | 557 | 1 | 312 | 1 | 0 | 1 |
| 557 | 312 | 1 | 245 | 0 | 1 | -1 |
| 312 | 245 | 1 | 67 | 1 | -1 | 2 |
| 245 | 67 | 3 | 44 | -1 | 2 | -7 |
| 67 | 44 | 1 | 23 | 2 | -7 | 9 |
| 44 | 23 | 1 | 21 | -7 | 9 | -16 |
| 23 | 21 | 1 | 2 | 9 | -16 | 25 |
| 21 | 2 | 10 | 1 | -16 | 25 | -266 |
| 2 | 1 | 2 | 0 | 25 | -266 | 557 |
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 ≡ 947 × 718-1 (mod 685) ≡ 947 × 602 (mod 685) ≡ 174 (mod 685)x ≡ 773 × 332-1 (mod 661) ≡ 773 × 221 (mod 661) ≡ 295 (mod 661)x ≡ 456 × 869-1 (mod 557) ≡ 456 × 291 (mod 557) ≡ 130 (mod 557)
So now we have the following equations of the form x ≡ a (mod m):
x ≡ 174 (mod 685)
x ≡ 295 (mod 661)
x ≡ 130 (mod 557)
Now the actual calculation
- Find the common modulus M
M = m1 × m2 × ... × mk = 685 × 661 × 557 = 252201245 - We calculate the numbers M1 to M3
M1=M/m1=252201245/685=368177,M2=M/m2=252201245/661=381545,M3=M/m3=252201245/557=452785 - 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 163 mod 685 ≡ 163n b q r t1 t2 t3 685 368177 0 685 0 1 0 368177 685 537 332 1 0 1 685 332 2 21 0 1 -2 332 21 15 17 1 -2 31 21 17 1 4 -2 31 -33 17 4 4 1 31 -33 163 4 1 4 0 -33 163 -685
Source: ExtendedEuclideanAlgorithm.com
So our multiplicative inverse is 67 mod 661 ≡ 67n b q r t1 t2 t3 661 381545 0 661 0 1 0 381545 661 577 148 1 0 1 661 148 4 69 0 1 -4 148 69 2 10 1 -4 9 69 10 6 9 -4 9 -58 10 9 1 1 9 -58 67 9 1 9 0 -58 67 -661
Source: ExtendedEuclideanAlgorithm.com
So our multiplicative inverse is -189 mod 557 ≡ 368n b q r t1 t2 t3 557 452785 0 557 0 1 0 452785 557 812 501 1 0 1 557 501 1 56 0 1 -1 501 56 8 53 1 -1 9 56 53 1 3 -1 9 -10 53 3 17 2 9 -10 179 3 2 1 1 -10 179 -189 2 1 2 0 179 -189 557
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
= (174 × 368177 × 163 +
295 × 381545 × 67 +
130 × 452785 × 368) mod 252201245
= 49111934 (mod 252201245)
So our answer is 49111934 (mod 252201245).
Verification
So we found that x ≡ 49111934
If this is correct, then the following statements (i.e. the original equations) are true:
718x (mod 685) ≡ 947 (mod 685)
332x (mod 661) ≡ 773 (mod 661)
869x (mod 557) ≡ 456 (mod 557)
Let's see whether that's indeed the case if we use x ≡ 49111934.