Answer:

1. 4 and 5

2. 8 and 9

3. 5 and 6

4. 6 and 7

5. 7 and 8

6. 16 and 17

7. 17 and 18

8. 6 and 7

9. 14 and 15

10. 4 and 5

11. 17 and 18

12. 15 and 16

13. 20 and 21

14. 15 and 16

15. 11 and 12

Step-by-step explanation:

1. √16 < √20 < √25

4 < √20 < 5

2. √64 < √77 < √81

8 < √77 < 9

3. √25 < √30 < √36

5 < √30 < 6

4. √36 < √38 < √49

6 < √38 < 7

5. √49 < √56 < √64

7 < √56 < 8

6. √256 < √280 < √289

16 < √280 < 17

7. √289 < √312 < √324

17 < √312 < 18

8. √36 < √45 < √49

6 < √45 < 7

9. √196 < √201 < √225

14 < √201 < 15

10. √16 < √21 < √25

4 < √21 < 5

11. √289 < √301 < √324

17 < √301 < 18

12. √225 < √227 < √256

15 < √227 < 16

13. √400 < √408 < √441

20 < √408 < 21

14. √225 < √237 < √256

15 < √237 < 16

15. √121 < √123 < 144

11 < √123 < 12