Nav computer: in the AIRSPEED window place the temperature (-30ºC) next to the Mach No. Index, go to Mach No. (0.83) on the inner main scale and read TAS next to it on the outer main scale: 503kts)  

Put 60 minutes on the inner main scale next to 503kts on the outer main scale, go to 360nm on the outer scale and read time (42.9 mins) next to it on the outer scale. N.b. zero wind so groundspeed = TAS.  

Aircraft needs to cover 360nm in 47.9 minutes (5 minutes longer than planned).  

Put 47.9 minutes on the inner scale next to 360nm on the outer scale; go to 60 (minutes) on the inner scale and read required groundspeed/TAS on the outer scale: 451kts.  

In the AIRSPEED window place the temperature (-30ºC) next to the Mach No. Index, go to TAS 451kts on the outer scale and read Mach No. next to it on the inner scale: M0.74.