2
The idea is to divide 20 / 2.
6 numbers can go into 20; they are 1, 2, 4, 5, 10 and 20.
20
2 times
2 goes into 6 three times. 2 goes into 20 ten times.
20 can go 4 times into 80
2 with remainder 15.
6 with a remainder of 2.
2 with remainder 4.
(6 and 1/2) times
100/5 = 20