### Brain Teasers

# Joe's Age

Math
Math brain teasers require computations to solve.

Joe's age plus 3 is a square number

Joe's age minus 3 is the square root

What is Joe's age?

Joe's age minus 3 is the square root

What is Joe's age?

### Answer

Joe is 6 years old6 + 3 = 9

6 - 3 = 3

3^2 = 9

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## Comments

OK

Brand-new teaser.

Credible. Fitting. Challenging.

How many comments?

Any bets?

I'll say ..................... fewer than five.

(not, of course, counting this one).

(that way I can't be accused of "influencing" the results) ....

So, you can lower your finger (the one that's poised over the "offensive" button).

Oh ... you folks are so much FUN !!!!!!!

YLADS (as ever)

BB02

Brand-new teaser.

Credible. Fitting. Challenging.

How many comments?

Any bets?

I'll say ..................... fewer than five.

(not, of course, counting this one).

(that way I can't be accused of "influencing" the results) ....

So, you can lower your finger (the one that's poised over the "offensive" button).

Oh ... you folks are so much FUN !!!!!!!

YLADS (as ever)

BB02

Very simple. It would have benefitted from a story to add some fun.

Sorry, Ghosty ......

Should have had higher rankings and ....

FIFTY !!!!!!!!!!!!!!!!!!!!

... comments.

But ..... everybody sez the reason is because I ... I ... I ... I... (as in ME) is here.

"Scaring" everybody off.

Do you believe that?

WHAT a bunch of C * * P.

There are other reasons why participation is so low, and we had better find them out and correct them or .....................

Braingle is DEAD DEAD DEAD

BB02

Should have had higher rankings and ....

FIFTY !!!!!!!!!!!!!!!!!!!!

... comments.

But ..... everybody sez the reason is because I ... I ... I ... I... (as in ME) is here.

"Scaring" everybody off.

Do you believe that?

WHAT a bunch of C * * P.

There are other reasons why participation is so low, and we had better find them out and correct them or .....................

Braingle is DEAD DEAD DEAD

BB02

2

2

2

2

2

2

That's right, folksies ...

TWO ....

A NEW Teaser comes and goes ... and we get ... TWO comments for the first day.

And some of you DARE to say

"all is well" .... and

accuse me of "sky is falling" tactics AND .....

Have me censured (loss of Karmas and privileges) ............

Proud of yourselves ????

BB02

2

2

2

2

2

That's right, folksies ...

TWO ....

A NEW Teaser comes and goes ... and we get ... TWO comments for the first day.

And some of you DARE to say

"all is well" .... and

accuse me of "sky is falling" tactics AND .....

Have me censured (loss of Karmas and privileges) ............

Proud of yourselves ????

BB02

Here I am ...

your NAKED "protest" ... "ant" ....

(what did you expect .... hmmmmm ??)

BB02

your NAKED "protest" ... "ant" ....

(what did you expect .... hmmmmm ??)

BB02

Perhaps an explanation would help.

I am a protestant (protest ... er) concerning the condition and health of Braingle. I protest about it, a LOT.

I am "naked" as in .... "devoid" ... (without, don't have, missing, etc.)

of defences or friends.

I'm doing it all by myself. Not a SINGLE other Braingle participant has "stepped up" to assist me.

But .... guess what?

I expected that.

Because a person in a "state of denial" will often "deny" that the "denial" even exists.'

Look in a mirror (some of you) ... if you want to see one.

YLADS (as ... always)

BB02

I am a protestant (protest ... er) concerning the condition and health of Braingle. I protest about it, a LOT.

I am "naked" as in .... "devoid" ... (without, don't have, missing, etc.)

of defences or friends.

I'm doing it all by myself. Not a SINGLE other Braingle participant has "stepped up" to assist me.

But .... guess what?

I expected that.

Because a person in a "state of denial" will often "deny" that the "denial" even exists.'

Look in a mirror (some of you) ... if you want to see one.

YLADS (as ... always)

BB02

Easy enough for Joe to solve it.

the given answer is easy. But did anyone find the other answer?

Joe can also be 1.

1 + 3 = 4

1 - 3 = -2

(-2) ^ 2 = 4

Joe can also be 1.

1 + 3 = 4

1 - 3 = -2

(-2) ^ 2 = 4

Simple to see when you set it up algebraically.

x is Joe's age.

(x - 3)^2 = x + 3

x^2 - 6x + 9 = x + 3 (expand left side)

x^2 - 7x + 6 = 0 (subtract right side from left side)

0 = (x - 6)(x - 1) (factor left side, and reverse)

The two solutions to zero the right side, forming a true statement are 6 and 1.

x is Joe's age.

(x - 3)^2 = x + 3

x^2 - 6x + 9 = x + 3 (expand left side)

x^2 - 7x + 6 = 0 (subtract right side from left side)

0 = (x - 6)(x - 1) (factor left side, and reverse)

The two solutions to zero the right side, forming a true statement are 6 and 1.

Excellent analysis & explanation ... eighssee ...

WELL DONE !!!!!

BB02

WELL DONE !!!!!

BB02

The way the teaser is phrased it says square root which is positive by definition. Therefore 1 is not an additional answer since sqrt(4) = 2 (not -2).

answer can be 6 or 1; @jimbo: sq rt of 4 is -2 or 2

Jimbo is actually correct. I had never been taught that "square root" specifically meant the positive. But then, what do you call it to mean + or -? Just "second root" or what?

2^2=4

(-2)^2=4

But

âˆš4=2

-âˆš4=-2

(-2)^2=4

But

âˆš4=2

-âˆš4=-2

So I guess the disconnect shows, for example, when you are solving an algebraic equation, like so:

x^2 = 4

{take "square root" of both sides}

x = +/- 4

WRONG!

x^2 = 4

{(1) take square root of both sides}

x = 4

{(2) OR, take negative square root of both sides}

x = -4

RIGHT!

x^2 = 4

{take "square root" of both sides}

x = +/- 4

WRONG!

x^2 = 4

{(1) take square root of both sides}

x = 4

{(2) OR, take negative square root of both sides}

x = -4

RIGHT!

I also got one as the age. I was thinking of bringing this to my group I do riddles with--they gave me the name "the riddler"--but I modified it following Gizzer's suggestion. So it begins, "Joe is learning about square roots. Being the type of kid that thinks about things a lot, he notices his age plus three is a square number, and his age minus three is the square root." OK, Six is young to learn about square root, but I know someone who was doing them at five. I like the story setting--thanks for the suggestion, Gizzer--and it makes the answer "one" less likely.

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