# Matrix multiplied by mod p

I was reading the following paper and I am stuck at the second last step. Can you please explain the L multiplied by (mod 19) step (right after (6))

How are they getting (3/5)mod 19 =12 ? similarly how are they getting the other matrix elements 16, 3, 12 ?

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## 1 Answer

The multiplicative inverse of 5 is 4 mod 19 like how the paper says. So instead of dividing by 5, you can just multiply by 4 and then reduce modulo 19 if the result is too large.

3*4=12

4*4=16

-4*4=-16=3 (mod 19)

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ok got it. thanks. –  Wildling Feb 20 '13 at 15:05