# phil1882

Members

570

## Community Reputation

13

• Rank
Senior Member

## Recent Profile Visitors

7223 profile views

## phil1882's Activity

1. phil1882 added a post in a topic numbers by the book

alright sorry, i tried to make it such that there was only 1 solution but looks like i failed. thanks for finding all 3.
• 0
2. phil1882 added a post in a topic if a,b,c, and d are natural numbers revisited.

yeap, or more specifically a power of 3.
• 0
3. phil1882 added a post in a topic if a,b,c, and d are natural numbers revisited.

i'm not going to list how to make each weight, however

• 0
4. phil1882 added a post in a topic numbers by the book

this solution doesn't work, as tim and fred both end in 2.
the numbers 1-5 should appear once in each digit place between men, as hint #2 tries to explain.

• 0
5. phil1882 added a topic in New Logic/Math Puzzles

numbers by the book
Five men, one of which is Greg each selected 5 unique 3 digit numbers from a hat. given the clues, can you tell what the numbers are and the men who selected them?
1. Each digit for the number chosen by each man is unique. (that is, if the number begins with 1, 1 wont appear anywhere else in the number.)
2. Each digit for each place between men is unique. (that is, if a number begins with 1, no other number begins with 1.)
3. Only the digits 1-5 are used.
4. Andy has the smallest number, and it's evenly divisible by 5.
5. Both Bob's and Fred's numbers are evenly divisible by 3.
6. Bob's number is smaller than Fred's.
7. Tim's number is evenly divisible by 2, and a prime.
8. Tim's number is greater than Bob's.
9. Fred's middle most number is prime.
10. Bob's middle and last number are odd.
11. the middle digit of Tim's number is twice as big as Andy's.

good luck and enjoy!
• 6 replies
• 86 views
6. phil1882 added a post in a topic if a,b,c, and d are natural numbers revisited.

7. phil1882 added a post in a topic Half as old as my brother

i was thinking it would be false if both were born on he same day, but even here it would be true, because they can't be born at exactly the same time.
• 0
8. phil1882 added a topic in New Logic/Math Puzzles

some 5 minute brain teasers
1. if all borks are grogs, and all grogs are snorts, are all snorts borks?
2. prove that GCD(A,B) = GCD(A+B,A) = GCD(A+B,B)
3. how much water, approximately, would you need to cover all land on earth in 3 feet of snow?
4. whats the shortest distance between any two points on a globe? A) straight line B) curved line
5. and just to be silly: what's the speed of dark?

• 958 views
9. phil1882 added a post in a topic Relatively prime

if you really wanna see something bizarre, the Riemann zeta function tells us that the sequence 1 +2 +3 +4 +5 .... = -1/12.
• 0
10. phil1882 added a post in a topic Relatively prime

the equation
1/1^2 +1/2^2 +1/3^2 ... is well known to be pi^2/6, and is equivalent to 1/(1-1/2^2) *1/(1-1/3^2) *1/(1-1/5^2) ...
• 0
11. phil1882 added a post in a topic Cosmetic Surgery and the Worm

12. phil1882 added a post in a topic Relatively prime

i'd take the bet.

• 0
13. phil1882 added a post in a topic A Complicated Numbers Problem

i had an idea of looking at the last three digits of powers of 5 and 3, but for 3 its not very good, its quite a long list. i'd say this problem is close to intractable.
or at least i dont see any good non mass calcuation solution to it for large powers.
• 0
14. phil1882 added a post in a topic A Complicated Numbers Problem

i have no idea how you could solve this without computing at least a few decimal points of sqrt(5).
for example one possiblility might be multipying by 3 -sqrt(5), but then i would have to divide by this number at the end of the problem.
the fastest way i know of, would be to compute about 1000 decimal points of 3+sqrt(5),
and then use the fact that a^n * a^n = a^(2*n). ie something like
v = 3 +sqrt(5) while n != 0:    if n&1 == 0:       n -= 1       v *= (3+sqrt(5))    else:       n >>= 1      v *= v print v
• 0