The price of 100 is 2.2× 100=220 yuan.
1) If n≤220
Bought: n/2.2=5n/ 1 1 piece.
2) if n > 220
I bought: (n-220)/2+100 = n/2-10+100 = n/2-10.
2.
0.48n≠5n/ 1 1
So I bought more than 100.
0.48n=n/2- 10
0.5n-0.48n= 10
0.02n= 10
n=500