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ErosOlmi
12-09-2013, 19:34
My son, 14 years old, his first day at high school.
Math hour, first question of the teacher:
when does 35 / 5 = 16 ?

:)

Michael Hartlef
12-09-2013, 19:38
Hu? Only when you write

35/5 = 1 + 6

Petr Schreiber
12-09-2013, 21:07
I think Mike got it,

I could not :D Well, actually I started to construct obscure theory of:
2^(3 + 5 / 5) = 16

...but for some reason I guess this is not it :D

Petr

ErosOlmi
12-09-2013, 21:12
There should be a law that prevents high school teachers from making parents look like idiots in front of their kids. :D
:D

Maybe I will just lose few karma points ;)

ErosOlmi
12-09-2013, 21:25
I too think Mike got it but the question would be quite silly.

Maybe it is just a silly question to decide who will sit in the first line of the class :)

peter
12-09-2013, 21:48
Hi,

1. If all teachers retire.

35/5 = 7
16*7 = 112
112 /7 =16

Petr Schreiber
12-09-2013, 21:49
I think it is excercise in lateral thinking (http://en.wikipedia.org/wiki/Lateral_thinking) (I didn't know this concept, till friend from work introduced me to the topic).

Here is example of another lateral thinking "puzzle" (a bit easier):
10+7=5
9+6=3
11+5=4
8+11=7

Petr

ReneMiner
12-09-2013, 22:35

ErosOlmi
12-09-2013, 22:42
Already done all the bases but it returns nothing close

ReneMiner
12-09-2013, 22:44

ReneMiner
13-09-2013, 06:43
another solution: when you add 45 before you divide

Is it maybe some wordplay?

ErosOlmi
13-09-2013, 07:13
Ok, time is over: my son is going to school.
If I will get the answer I will let you know.

Thanks to all.
Eros

Michael Hartlef
13-09-2013, 08:59
Yes, please let us know. I am curious what the answer will be. So many time these i am puzzled about what the kids get asked these days. They have changed a lot. The grammar, the spelling, the methods how math has to me done, etc.i

ErosOlmi
13-09-2013, 15:15
Well ... :oops:
I'm a little bit embarrassed to say that the question had nothing to do with math, damn!
The teacher was referring to an Italian television program of the 60th in order to demonstrate something that my son reported as: "I didn't understand anything"

So, sorry for letting you lose time on this.

The only positive aspect I can get from this post is that you are all great in participating so nicely to the life of this forum :)
And for this I will be forever grateful.

Eros

ReneMiner
13-09-2013, 15:43
Really funny how such misunderstandings made our brains smoking.
8533

Gerald Sutherland
13-09-2013, 16:22
Even though the challenge is over and the question wasn't math based ... I had one of those "from another planet" thoughts this morning and regardless of it's truth ... I'd like to submit another possibility. Mixed bases. Assume Base 25 for the left side of the equation and Base 10 for the right side. Then 35 (base 25) becomes 80 (base 10), 5 remains 5 ... so ... 80/5 (base 10) = 16 (base 10). Ok, no laughing. :D

ErosOlmi
13-09-2013, 17:16
That's it!
GREAT

:drink:

ErosOlmi
13-09-2013, 21:41
Last chapter of the story: I think Petr got it

I think it is excercise in lateral thinking (http://en.wikipedia.org/wiki/Lateral_thinking) (I didn't know this concept, till friend from work introduced me to the topic).

I came back from work and talked with my son: he had a little bit more desire to talk than before :)

The story is this:

during a TV show a guy not really well educated was asked what was the the result of 35/5
he replied 16
the presenter replied why 16?
well if you divide 5 by 5 it gives 1 with rest of 0
then you divide 30 by 5 and it gives 6
so the answer is 16 (the guy was dividing 35 by 5 considering 35 from right to left and not from left to right)
the presenter said: but if you multiply 16 by 5 it doesn't give 35
the guy said: yes it gives 35 and here is the proof (he wrote down 5 times 16 in vertical mode)

16
16
16
16
16
if you vertically sum all the 6 it gives 30 (5 times 6)
if you vertically sum all the 1 it gives 5 (5 times 1)
30 + 5 = 35

Wow!

So the moral is that my son teacher wanted to explain that there are many and different ways to see reality, not just the correct one.

I think at the end it was not a bad first day school approach.

Hope the teacher will accept from my son a similar explanation when he will try to explain why he missed to correctly calculate an equation.
:D

Petr Schreiber
13-09-2013, 22:19
Hehe,

thanks for the solution. It would never occur to me to divide this way, but I must admit division with rest always gives my brain 100% CPU usage :)

Petr

Charles Pegge
13-09-2013, 23:52
Division is hard for CPUs too. Successive approximation is the only way so it is about 30 times slower than multiplying.

Charles Pegge
14-09-2013, 10:38
No, addition, subtraction and also multiplying appear to be single step.

kryton9
14-09-2013, 11:29
This is very interesting. Here is my take after reading all the posts.

Our logic 35 / 5 = 7 or in other words 7(fives) equals a total of 35
Step 1:
1. 5
2. 5
3. 5
4. 5
5. 5
6. 5
7. 5
-----
35

His alternate logic from now on carried to the full answer:
Step 2: now take away 1 of the fives and write down 1
this leaves 6 fives, write down 6 ending up with 16:
1. 5
2. 5
3. 5
4. 5
5. 5
6. 5
-----
16 = 1(five) + 6(fives) = 5 + 30 = 35

Now take this further:
Step 3. Take away 2 of the fives and write down 2
this leave 5 fives, write down 5 ending up with 25:
1. 5
2. 5
3. 5
4. 5
5. 5
------
25 = 2(fives) + 5(fives) = 10 + 25 = 35

So this carries out with the logic to the next step
34 = 3(fives) + 4(fives) = 15 + 20 = 35
43 = 4(fives) + 3(fives) = 20 + 15 = 35
52 = 5(fives) + 2(fives) = 25 + 10 = 35
61 = 6(fives) + 1(five) = 30 + 5 = 35

The correct answer by the teacher using this logic should have been:
35 / 5 = the set of {16, 25, 34, 43, 52, 61} and not 35 / 5 = 16

A note of interest: the difference between all of the numbers in the set is a difference of 9:
16 + 9 = 25
25 + 9 = 34
34 + 9 = 43
43 + 9 = 52
52 + 9 = 61

35 / 7 using the numbers 3, 5, and 7 : 5+7 = 12: 12 -3 = 9
or perhaps a better way to look at it.
There are 7(fives) so write a 7
now the difference between 7 and 5 = 2, so add this to the 7: 7 + 2 = 9

Voodoo Math enough for today :)

Update, thinking of this stuff on second night sleep:
The 9 difference comes not from those voodoo equations but because of the decimal number system 0-9.
Here is how it works:
A / B = C
1. A has to be bigger than B
2. C has to be a whole number
3. The number of elements in the resulting set is C+1
4. The first element in the resulting set is C
5. Each subsequent element is the previous element plus
9 for single digit results or remainders\
99 for 2 digit results or remainders
999 for 3 digit results or remainders and so on.

The first digit in the resulting element is the "take away number" the second numbers is the "remaining numbers"

So in doing this my first answer set was missing 2 elements:
Here is what I wrote wrongly and now on second night of sleep it all became clear.
The correct answer by the teacher using this logic should have been:
35 / 5 = the set of {16, 25, 34, 43, 52, 61} and not 35 / 5 = 16

As you see I should have had C + 1 elements and the first element should have been C
A / B = C 35 / 5 = 7 so I should have 7+1 or 8 elements instead of my original 6
and the first element should be C or 7, so the correct answer is:
35 / 5 = 7 our logical math and in lateral logic math the set of { 7, 16, 25, 34, 43, 52, 61, 70 }

1. 5
2. 5
3. 5
4. 5
5. 5
6. 5
7. 5
-----
35

if you take away 0 (fives) your first digit it 0
the remainder is 7(fives) so your second digit is 7
07 = 7, this is your first element.

the last element is you take all 7(fives) your first digit is 7
the remainder is 0(fives), this is your second digit 0
70 and so this completes the set.

What is funny is that A and B can be decimal values, as long as A > B and C is a whole number it works.

1.25 / 0.25 = 5 so the resulting set will be 6 elements long starting with 5
1. 0.25
2. 0.25
3. 0.25
4. 0.25
5. 0.25
--------
1.25
take away 0 remainder 5 = 05 = 5
take away 1 remainder 4 = 14 = 5+9
...
take away 5 remainder 0 = 50
{5, 14, 23, 32, 41, 50}

Last one:
1353 / 123 = 11 since 2 digits will be +99 till we get to single digits then +9
take away remainder result
1. 123 11 0 110
2. 123 10 1 101
3. 123 9 2 92
4. 123 8 3 83
5. 123 7 4 74
6. 123 6 5 65
7. 123 5 6 56
8. 123 4 7 47
9. 123 3 8 38
10. 123 2 9 29
11. 123 1 10 110
0 11 11
{11, 110, 29, 38, 47, 56, 65, 74, 83, 92, 101, 110 }

kryton9
14-09-2013, 21:08
Black and white, dark energy and energy, matter and anti matter and now voodoo math just wanted to bump my post, I updated it after waking up.