An air craft is cruising at 10,000 ft density height in a 20kts head wind has an indicated air speed of 175 kts . if the fuel flow is 20 US gallons per hour, the specific air range is closest to?
a) 0.29 kg/nm
b) 0.31 kg/nm
c) 0.10 kg/nm
d) 0.27 kg/nm

The correct answer is 0.27 kg/nm

Can anyone explain further how we get the answer 0.27kg/nm?

Given

IAS = 175 kts
DH = 10,000' ---> TAS = 204 kt

FF = 20 usg/hr

For specific air range:

SAR = FF/TAS
= 20/204 usg/nm
= (20 x 2.72)/204 kg/nm
= 0.27 kg/nm ( 2 sig. figures)

If asked for specific ground range SGR

SGR = FF/GS

Just as an aside, specific air range is usually calculated as

SAR = TAS/FF ( the units are then, nm/kg)

Thank you very much..very clear and understandable