Time Conversions?

I'm working on a sheet for flight planning.

A1: Speed in kts (nautical miles / hour)
B1: Distance in nautical miles
C1: Time
D1: Fuel Burn (litres / hour)
E1: Fuel Required

eg..

A1 = 120, B1 = 60, C1 = (60/A1*B1)/60, D1 = 60, E1 = D1 * C1

that works....

However!... Currently the display in C1 is "0.5" as in 0.5 hours (30 minutes). I'm looking to have it display 00:30 (hours:minutes).

if I try setting the cell format to hh:mm I get 12:00

PLEASE HELP!!

TIA