If 10.5 is supposed to be 10:30 then all you have to do is divide by 24
Format result cells as time:
Excel 2010
<colgroup><col style="width: 25pxpx"><col><col></colgroup><thead>
</thead><tbody>
[TD="align: center"]1[/TD]
[TD="align: right"]11.00[/TD]
[TD="align: right"]11:00 AM[/TD]
[TD="align: center"]2[/TD]
[TD="align: right"]10.50[/TD]
[TD="align: right"]10:30 AM[/TD]
</tbody>
Sheet1
[TABLE="width: 85%"]
<tbody>[TR]
[TD]
Worksheet Formulas[TABLE="width: 100%"]
<thead>[TR="bgcolor: [URL=https://www.mrexcel.com/forum/usertag.php?do=list&action=hash&hash=DAE7F5]#DAE7F5[/URL] "]
[TH="width: 10"]Cell[/TH]
[TH="align: left"]Formula[/TH]
[/TR]
</thead><tbody>[TR]
[TH="width: 10, bgcolor: [URL=https://www.mrexcel.com/forum/usertag.php?do=list&action=hash&hash=DAE7F5]#DAE7F5[/URL] "]B1[/TH]
[TD="align: left"]=A1/24[/TD]
[/TR]
[TR]
[TH="width: 10, bgcolor: [URL=https://www.mrexcel.com/forum/usertag.php?do=list&action=hash&hash=DAE7F5]#DAE7F5[/URL] "]B2[/TH]
[TD="align: left"]=A2/24[/TD]
[/TR]
</tbody>[/TABLE]
[/TD]
[/TR]
</tbody>[/TABLE]
If however 10.50 is supposed to be 10:50 AM, then perhaps:
=SUBSTITUTE(A1,".",":")+0
Format as time.
Excel 2010
<colgroup><col style="width: 25pxpx"><col><col></colgroup><thead>
</thead><tbody>
[TD="align: center"]1[/TD]
[TD="align: right"]11.00[/TD]
[TD="align: right"]11:00 AM[/TD]
[TD="align: center"]2[/TD]
[TD="align: right"]10.50[/TD]
[TD="align: right"]10:50 AM[/TD]
</tbody>
Sheet1
[TABLE="width: 85%"]
<tbody>[TR]
[TD]
Worksheet Formulas[TABLE="width: 100%"]
<thead>[TR="bgcolor: [URL=https://www.mrexcel.com/forum/usertag.php?do=list&action=hash&hash=DAE7F5]#DAE7F5[/URL] "]
[TH="width: 10"]Cell[/TH]
[TH="align: left"]Formula[/TH]
[/TR]
</thead><tbody>[TR]
[TH="width: 10, bgcolor: [URL=https://www.mrexcel.com/forum/usertag.php?do=list&action=hash&hash=DAE7F5]#DAE7F5[/URL] "]B1[/TH]
[TD="align: left"]=SUBSTITUTE(
A1,".",":")+0[/TD]
[/TR]
[TR]
[TH="width: 10, bgcolor: [URL=https://www.mrexcel.com/forum/usertag.php?do=list&action=hash&hash=DAE7F5]#DAE7F5[/URL] "]B2[/TH]
[TD="align: left"]=SUBSTITUTE(
A2,".",":")+0[/TD]
[/TR]
</tbody>[/TABLE]
[/TD]
[/TR]
</tbody>[/TABLE]