I'll do the first one..you should be able to do the rest..we will use the "divide and average" method
Let us suppose that we think 3 is the sq rt of 20
1. Divide 20 by 3 = 6.66
2. Average 3 + 6.66 = (3 + 6.66) / 2 = 4.83
3. Divide 20 by 4.83 = 4.14
4. Average 4.83 and 4.14 = ( 4.83 + 4.14) / 2 = 4.485
5. divide 20 by 4.485 = 4.459
6. Avverage 4.485 and 4.459 = 4.472
7. Divide 20 by 4.472 = 4.472
The last two results agree to two decimal places
So.....sqrt 20 ≈ 4.47