I am not to good with Excel.

I have to make up a time sheet. Right now my "total weekly hours" box has a
time format of 'h:mm'. I need to calculate that by and hourly rate and then
into the dollar figure. Everytime I trie I get a very small fraction of the
actual dollar amount. Can someone help me?

an example: I worked 11:30 (11 and a 1/2 hours) at $15.00/hr. That should
equal $172.50 but Excel says it equals $7.19. I know I need to probably
convert the 11:30 to 11.5hrs but how?

Thanks in advance for the help