Use the digits from 1 up to 9 and make 100.

Follow the rules.
=> Each digit should be used only once.
=> You can only use addition.
=> For making a number, two single digits can be combined (example, 4 and 2 can be combined to form 42 or 24)
=> A fraction can also be made by combining the two single digits (example, 4 and 2 can be combined to form 4/2 or 2/4)

Question: how can we do this ?

There are various solutions that one can come up with. Following are some of them.
1 + 2 + 5 + 4/6 + 7/3 + 89 =100
12 + 9 + 75 + 6/3 + 8/4 =100
2 + 95 +1/6 + 4/8 + 7/3 =100
24 + 57 + 8 + 6/3 + 9/1 =100
36 + 51 + 9 + 4/8 + 7/2 =100
5 + 91 + 3/2 + 6/8 + 7/4 =100