You may want to read about Congruences before doing this worksheet.

- Find the least residue of 1215 (mod 4), (mod 10), and (mod 100).
- Find the least residue of 1867 (mod 4), (mod 10), and (mod 100).
- If k ≡ 1 (mod 4), then what is 6k + 5 congruent to (mod 4)?
- To what values (mod 30) can prime numbers greater than 5 be congruent? (Hint: 30 = 2 × 3 × 5).