Some math riddles...

[VJ]

Well, hope everyone had a Merry Christmas ! (apparently, half my family got ill the day after, but they all seem to be bettering now )

Time again for some math riddles ?

1. Fill in numbers between 1 though 7 (7 included) on the spots marked by X, such that
- the given numbers are the sum of the numbers in the surrounding spots
- no row/column contains the same number twice:

x x x x x x x
x 26 x 35 x 37 x
x x x x x x x
x 31 x 36 x 39 x
x x x x x x x
x 38 x 26 x 24 x
x x x x x x x

(it should be a square, 7x7 in size)

2. Complete the sequence
1 3 5 7 9 15 17 21 31 33 ??
(there is a small hint: "think simple, we find decimal too difficult")

Have fun!


Jörg

[cjolley]

One answer to #2 is 37 (pattern is 2222422224 etc)

I'm not even going to attempt the second.
chuck

[VJ]

Originally posted by cjolley
One answer to #2 is 37 (pattern is 2222422224 etc)

Could you explain that pattern ? (I was thinking along the lines of binary numbers - because of the hint : all numbers are symmetric in binary notation, but I could not find a common pattern among them)
The difference between 9 and 15 is 6 ...

Jörg

[cjolley]

Originally posted by VJ
Could you explain that pattern ? ....The difference between 9 and 15 is 6 ...

Jörg

No
Well, yes. I didn't get much sleep last night.
chuck

[lurqa_MU]

Re: Some math riddles...

Originally posted by VJ

2. Complete the sequence
1 3 5 7 9 15 17 21 31 33 ??
(there is a small hint: "think simple, we find decimal too difficult")

If we study the numbers in binary notation they almost form a pretty neat pattern:

01=00000001
03=00000011
05=00000101
07=00000111
09=00001001
15=00001111
17=00010001
21=00010101
31=00011111
33=00100001
xx=00111111 = 63

The only problem is that 21 does not fit very well into the pattern.

Regards,
lurqa

[cjolley]

Re: Re: Some math riddles...

Originally posted by lurqa_MU
If we study the numbers in binary notation they almost form a pretty neat pattern:

01=00000001
03=00000011
05=00000101
07=00000111
09=00001001
15=00001111
17=00010001
21=00010101
31=00011111
33=00100001
xx=00111111 = 63

The only problem is that 21 does not fit very well into the pattern.

Regards,
lurqa

almost

01=1
03=11
05=101
07=111
09=1001
15=1111
17=10001
21=10101
31=11111
33=100001
xx=101101 = 45

chuck

[KvHagedorn]

Re: Some math riddles...

Originally posted by VJ

1. Fill in numbers between 1 though 7 (7 included) on the spots marked by X, such that
- the given numbers are the sum of the numbers in the surrounding spots
- no row/column contains the same number twice:

x x x x x x x
x 26 x 35 x 37 x
x x x x x x x
x 31 x 36 x 39 x
x x x x x x x
x 38 x 26 x 24 x
x x x x x x x

(it should be a square, 7x7 in size)

2. Complete the sequence
1 3 5 7 9 15 17 21 31 33 ??

Heh.. no.

[VJ]

cjolley: That is what I was thinking... Still strugling with the first one though...
kvhagedorn: I like the contradiction between the smiley and the "kind regards"...


Jörg