[Math] How to find out which number is larger without a calculator

algebra-precalculusarithmeticexponentiationinequality

So I have a question which is:

Which is larger?

$$2.2^{3.3} \text{ or } 3.3^{2.2} $$

Now I need to find out with using a calculator but the answer is $3.3^{2.2}$.

The only thing I could think of is rounding.

So you know:

$2^3=8$ and $3^2=9$

I'm interested in seeing if there are other ways just because there might be the possiblity of being asked:

Which is larger?

$$2.5^{3.5} \text{ or } 3.5^{2.5} $$

So if I use the rounding idea, would I just round normally. I would get:

$$ 3^4 \text{ or } 4^3 $$

which shows $3^4$ is larger.

This is the only way I could think of, are there any other ways without using a calculator to determine which is larger?

Best Answer

$$2.2^{3.3}\gtrless3.3^{2.2}$$ $$(2.2^3)^{1.1}\gtrless (3.3^2)^{1.1}$$ $$2.2^3\gtrless 3.3^2$$ $$(2\cdot 1.1)^3\gtrless (3\cdot 1.1)^2$$ $$2^3\cdot 1.1\gtrless 3^2$$ $$8\cdot 1.1\gtrless 9$$ $$8.8<9.$$

So, $$2.2^{3.3}<3.3^{2.2}.$$


Can you find now which number is larger: $2.25^{3.375}$ or $3.375^{2.25}$ ;) ?

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