Add, subtract and multiply square roots of perfect squares

Find the positive number that multiplied by itself gives the number inside the root.

1. Evaluate √121 + √36.
2. Evaluate √36 − √36.
3. Evaluate √36 − √49.
4. Evaluate √100 − √144.
5. Evaluate √49 + √25.
6. Evaluate √25 + √16.
7. Evaluate √196 × √9.
8. Evaluate √9 × √144.
9. Evaluate √256 × √100.
10. Evaluate √361 − √400.
11. Evaluate √64 − √121.
12. Evaluate √289 × √361.
13. Evaluate √49 + √289.
14. Evaluate √256 × √25.
15. Evaluate √81 × √441.
16. Evaluate √625 + √625.
17. Evaluate √169 + √841.
18. Evaluate √529 − √676.
19. Evaluate √441 × √64.
20. Evaluate √9 − √25.