Simply because the solution to your sum produces a repeating decimal. Just as 22/7 (The value of Pi as a fraction) produces the repeating decimal 3.142857
1.625
39 / 4 = 9.75
9.6662
6.33333 repeating or rounded to 6.3
5.5714
19.9286
4.3333
-39
2.5641
Equal to it 39 divided by 20 is 1.95. It is probably quicker to use a calculator than to ask on line
7.8
507 divided by 39 is 13.