"How to say '一个半小时' in English?"
In English, "一个半小时" is translated as "one and a half hours". This can be written as "1.5 hours" or even more succinctly as "1 1/2 h".
If you want to express the idea of half an hour in a more concise way, you can use the phrase "30 minutes" followed by "half", as in "30 minutes and a half". This can be abbreviated to "30m+1/2h" or even further shortened to "30m+fh" (where "fh" stands for "half").
