If you have a CR-2/3
Find the ISA temperature at FL350 = -55
Go to the Mach Index window on your CR-3 and line up -55.
On the Gray outer scale of your CR-2/3 (which you would normally use for minutes in a fuel flow calculation) line up 82 (which is Mach 0.82) The outer scale will show a TAS of 470kts
SAR = 470/4410*1000
SARs are pretty useless, SGRs are used everyday and something you will be using a lot in Flight Planning.
Good Luck.