How fast are the blades in a jet engine turning at full throttle?

There are many different engine options on the 747 -

I only know the "Classics" - 100-200-300-SP -

They can be fitted with P&W JT9D - GE CF6 or RR RB211 -

All have different versions (dash numbers) from 43,500 to 53,000 lbs thrust -

A JT9D-7Q engine shafts RPM is 3,600 RPM for N1 and 7,800 RPM for N2 -

Maximum % RPM is 104.2% N1 and 102.5% N2 -

These engines are 52,000 lbs thrust (-7Q) -

Fuel flow at sea level for that thrust is 19,900/hr lbs fuel flow -

TSFC thrust specific fuel consumption is .378 lbs FF -

Bypass ratio - 4.9 : 1 -

Fan thrust 41,000 lbs - core thrust 11,000 lbs -

Mass airflow 1,678 lbs of air per second -

You need to research the GE and RR engines -

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The RPM depends on the length of the blades themselves. A shorter blade will rotate at a higher RPM and a longer blade will rotate at a slower RPM. This is due to the fact that the blades should not approach the speed of sound due to compressibility. Compressibility drastically reduces performance of an airfoil. The longer the blade is, the tips of the blade rotate a further distance which equates to a faster speed. So it all depends on the length of the blade. The turbine blades inside of a jet engine should never approach the speed of sound.

Depends on the engine manufacturer and which blades (high bypass fan N1 or core compressor N2) you are talking about. The Pratt & Whitney 4000 series have max N1 rpms of around 4000, and max N2 Rpms around 10,000. General Electric CF6s on most of the 747-400s is about the same, with a little higher on N2 speed at about 11,000 RPM. Rolls Royce probably very similar.

9900 Rpm

2100 & 2200 RPM