Friday, January 15, 2010

How Old?

If you transpose the digits of Abe's age, you get Bill's age. The difference between Abe's and Bill's ages is twice Claude's age. Bill is ten times as old as Claude.

What color is the bear? ... oh wait ... wrong problem. What are the ages?

16 Comments:

Anonymous Anonymous said...

They are all 0

Cam

January 15, 2010 8:10 PM  
Anonymous Anonymous said...

or just Claude is 0

Cam

January 15, 2010 8:13 PM  
Anonymous Anonymous said...

A=54,B=45,C=4.5 works if fractional age of Claude is allowed

Cam

January 15, 2010 8:27 PM  
Blogger Chris said...

Haven't got the answer (and shan't tonight) but Abe and/or Bill must be over a 100 years old. Otherwise Cam is right.

January 15, 2010 8:29 PM  
Blogger Chris said...

... assuming integer ages.

January 15, 2010 8:30 PM  
Blogger Chris said...

LOL, 540, 450 and 45 does it(thanks Cam).

January 15, 2010 8:33 PM  
Blogger Chris said...

I guess Abe, Bill and Claude are trees.

January 15, 2010 8:55 PM  
Anonymous Anonymous said...

How Old ?
Assume <100 years old
10x+y=A
10y+x=B
where x an y are integers from 0 to 9
A-B=9x-9
So if A>B
9x-9y=2C
x=2/9*C+y
B=10C
10y+x=10C
sub in x eq
10*y+2/9*C+y=10C
11y=(10-2/9)C
11y=88/9*C
y=8/9*C
so if C=9 y=8
then from 10y+x=10C we have 80+x=90
x=10 ??, x must be from 0 to 9
if fractional age of C allowed
C=9/8*y
10y+x=10C
x=10*(9/8*y)-10*y=10/8*y
try y=0 to 9 to find integer solutions <=9 for x
y=0 x=0 trivial
y=4 x=5
so A=54,B=45, C=4.5

Test if B>A
9x-9y=-2C
x=-2/9*C+y
B=10C
10y+x=10C
sub in x eq
10*y-2/9*C+y=10C
11y=(10+2/9)C
11y=92/9*C
y=92/99*C
if fractional age of C allowed
C=99/92*y
10y+x=10C
x=10*(99/92*y)-10*y=70/92*y
try y=0 to 9 to find integer solutions <=9 for x
y=0 x=0 trivial
no integer solutions

Answer:
If fractional age for Claude is allowed
Abe=54,
Bill=45,
Claude=4.5

Cam

January 15, 2010 8:58 PM  
Anonymous Anonymous said...

Why stop at tress ? Why not make them stars ?
Abe 54*10^12, Bill 45*10^12, Claude 4.5*10^12

Cam

January 15, 2010 9:07 PM  
Anonymous Zaux said...

nothing wrong with someone being 4.5 years of age ... good job Cam... as usual

January 15, 2010 9:58 PM  
Blogger Chris said...

infinity, infinity and infinity.

January 15, 2010 11:14 PM  
Blogger Chris said...

Assuming Bill older than Abe:
10y + x - (10x + y) = 0.2(10y + x)
9y - 9x = 0.2(10y + x)
45y - 45x = 10y + x
35y = 46x
(5*7)y = (2*23)x
x = 35, y = 46 is the smallest solution (in the positive integers), so Bill cannot be older than Abe.

Therefore, Abe must be older than Bill =>
(10x + y) - (10y + x) = 0.2 (10y + x)
9x - 9y = 0.2 (10y + x)
45x - 45y = 10y + x
44x = 55y
4x = 5y
=> x = 5, y = 4 is the only possible solution if the ages are less than 100.
So Abe is 54, Bill is 45 and Claude is 4.5 is the only possible answer for Abe and Bill < 100.

January 16, 2010 1:01 AM  
Blogger Chris said...

small slip. I've assumed Abe and Bill have an integral age.
5.4, 4.5 and 0.45 also work. The question makes it vaguely clear (I jest) that Abe and Bill have ages that must be repesented with two digits.

At a pinch could say, .54, .45 and 0.045. I think 0.54, 0.45 would be pushing it a bit.

January 16, 2010 1:28 AM  
Blogger Chris said...

Hi Zaux. Despite been miffed at the non-integral value of Claude's age (I do accept that that is fair), I think it was a fine problem. Thank you for posting it.

January 16, 2010 2:41 AM  
Anonymous Anonymous said...

I know the answer!! the bear is purple!!! lol to much math!

:P

January 16, 2010 1:24 PM  
Blogger Chris said...

...noooooo. The unicorns were purple. The bear was brown.

January 16, 2010 2:20 PM  

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