walker
Is \(4^{\frac12}+4^{\frac13}+4^{\frac14}\) greater than 5?
I'm interested in the fastest approach. So, don't forget to start your timer

I've tried to get it down to a point where you'd need to round only once. I think that's very important under given conditions. Actually, it was due to rounding that guys ended up with different answers.
assume \(4^{\frac12}+4^{\frac13}+4^{\frac14}>5\)
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\(4^{\frac13}+4^{\frac14}>5-2\)
\(2^{\frac23}+2^{\frac12}>3\)
\(2^{\frac23}>3-2^{\frac12}\)
take it to the power of 3
\(2^2>(3-2^{\frac12})(3-2^{\frac12})(3-2^{\frac12})\)
\(4>(9-3*2*2^{\frac12}+2)(3-2^{\frac12})\)
\(4>(11-6*2^{\frac12})(3-2^{\frac12})\)
\(4>(33-18*2^{\frac12}-11*2^{\frac12}+12)\)
\(4>(45-29*2^{\frac12})\)
and this is the point when you have to be cautious rounding \(sqrt(2)\)
if you take 1.4 you will get the wrong answer. If, however, you multiply 1.414 by 29 you will see that the inequality holds true under given assumption.