Hi Thomas:
With your times in A1 and B1, in C1 enter:
=(B1-A1)*24 and format this cell as General will return 1.5
FYI: Excel treats time as a part of a 24 hour day, hence the result of your formula B1-A1 needs to be multiplied by 24 to convert to hours/parts of hour.
To test, try this: In D1 enter =A1*24 and format as General or Number w/2 decimals. The result will be 10.75 (which is, of course, 10 hours and 45 minutes as a decimal). Also, try changing the format of B1 to Number and see: 0.51 (which shows that 12:15 PM is just past half of a 24 hour day.
HTH
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