The Puzzler – Week 24

Welcome to The Puzzler. Every week, there are 2 new puzzles related to my passion: math, logic, and thinking. The first puzzle will be The Puzzler Quik, meant for those who crave something fun-sized. The second puzzle will be The Puzzler Think, meant for those who love to ponder. The answers will be posted in next week’s column. Don’t forget to submit your answer for a potential shout-out in the next edition of the Puzzler.
 
 

Puzzler Quik

Can you simplify this expression? $$\log_{23}{23} + \log_{23}{1} + \log_{16}{256}?$$

Puzzled?

Don’t know what Logarithms are? Tune out for our upcoming video on them!

Try simplifying each log seperately!

Puzzler Think

What is the value of $a$ for which $\frac1{\log_2a}+\frac1{\log_3a}+\frac1{\log_4a}=1$ ?

Puzzled?

Don’t know what Logarithms are? Tune out for our upcoming video on them!

Try making the base common in all 3 logarithms!

Last Week's Puzzler Quik

Anay from Portland, Oregon was the winner of this shout-out.

There is a formula for this! $$\frac{n(n+1)(2n+1)}{6}$$ Plugging in 100 for “n”, we get $$\frac{100\cdot101\cdot201}{6} = 338350.$$

Our answer is 338350!!!

Want a proof for this formula? Here is a good link! https://proofwiki.org/wiki/Sum_of_Sequence_of_Squares

Last Week's Puzzler Think

This week’s shout out goes to Chirag from Arkansas! Kudos to him!

Here is his awesome explanation: 

It is well-known that the sum of an infinite geometric series is $$\frac{a}{1-r}$$

But nothing is good without a proof. So here is one.

Let $$a + ar + ar^2 + … = S.$$ Thus, $$ar + ar^2 + ar^3 + … = S\cdot{r}$$ Subtracting this equation from the first equation, we have $$a = S – Sr => a = S(1 – r).$$ Dividing both sides by 1 – r, $$\frac{a}{1 – r} = S.$$ In this case, a = 1/2 and r = 1/2, so substituting it into the formula, $$S = \frac{\frac{1}{2}}{1 – \frac{1}{2}} = \frac{\frac{1}{2}}{\frac{1}{2}} =1.$$ We have proved that $$\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+… = 1.$$

We are done!

1 thought on “The Puzzler – Week 24”

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