As mentioned above by Nebu, this Nexus 9 Geekbench 3 data appears to be using AArch32. So measuring using AArch64 should give a huge boost to some of the floating point numbers.
When Anandtech reviewed the iPhone 5s, moving from AArch32 test to AArch64 test in Geekbench 3, they measured an improvement of +25% in BlackScholes, +16% in Blur Filter, +195% in DGEMM, +119% in SFFT, +26% in N-Body, +51% in RayTrace (
http://www.anandtech.com/show/7335/the-iphone-5s-review/4 )
Here is a Geekbench 3 comparison between HTC Volantis Nexus 9 and iPhone 5s, both using AArch32:
http://browser.primatelabs.com/geekbench3/compare/1014854?baseline=1002621
The single-core performance in this comparison is 80-90% higher than first gen Cyclone! Now, exactly how much improvement there will be from AArch32 to AArch64 with the Denver core is unknown at this time (the Cyclone core shows an improvement of ~ 35% overall). It is also unclear exactly what CPU clock operating frequency is being used for the Denver cores benchmarked here.
At Hot Chips, Denver was said to have a Geekbench 3 single-core score that was ~ 1.65x higher than R3 Cortex A15 in Tegra K1, and ~ 1.375x higher than Cyclone in A7 iPhone 5s. So I don't know exactly what to make of these two new AArch32 data points. The only way for these numbers to make sense is if NVIDIA showed AArch32 Geekbench 3 data for Denver at Hot Chips while comparing it to AArch64 Geekbench 3 data for Cyclone.