Ultimate math trick question?

[DevilsAdvocate]

Hold up.

You were born midnight 1/1/1980. At midnight 1/1/1984 you turn 4. That's 1461 days old. She's half as much at 730.5 days. So she was born noon 12/31/1981. At noon 12/31/1993, she turns 12. You are still 13 until the next day-12 hours away. On 12/31/1993 she is 12 and you are 13

 

[Loss Leader]

Oh, that's stupid. That is just ... so stupid.

To expand on the stupidity ...

Why are you only using the Western colloquial definition of "four years old"? There are plenty of societies that count a person's age from the point of conception or that just declare that all people to have been born on January 1st.

Even in the West, we do that. If a baby is born on December 31, the parents get to write him off as a dependent for the whole year. So the IRS considers all children to be born on the previous January 1. it also considers all children to turn 18 on the next January 1 after their birthday.

Also, the Gregorian calendar isn't the only one in use in the world. In the Chinese calendar an ordinary year has 353, 354, or 355 days, a leap year has 383, 384, or 385 days. That's about the same for the Hebrew calendar.

What does that do to your math? It borks it completely is what it does. You choose some unstated premises to accept (like the western calendar and the western way of marking birthdays) while choosing some unstated premises to reject (like 4 meaning 4). You provide no justification for doing so, but insist that you have the "right" answer.

You don't. Your answer is, as said, stupid.

 

[Modified]

Even in the West, we do that. If a baby is born on December 31, the parents get to write him off as a dependent for the whole year.

I wonder how many medically induced births occur to cash in on those tax savings.

 

[Loss Leader]

I wonder how many medically induced births occur to cash in on those tax savings.

At least some Eastern couples have scheduled c-sections for days they consider "lucky" like 8 or 3.

 

[DevilsAdvocate]

Sheesh. Tough crowd.

The answer of 14 is correct in a general sense. Considering that "years old" generally means an age spanning a year, that creates an interesting math problem. The answer of 14-15 is basically correct. It doesn't account for leap years, which is important when considering how many "years old" someone is.

I should have put my answer in years and days instead of a decimal percent of years.

The correct answer is 13 years 364 days to 15 years 182 days.

For the alternative interpretation, 13 years 1 day to 15 years 364 days.

 

[theprestige]

[emoji106][emoji106][emoji106]

a person who is "4" is actually between "4" and "4 years+364 days" due to always rounding down.

So the sister will be between "2" and "2 years 182 days" younger, being half your age.

wait til sis becomes 12, then you are between 14 and 14 years +182 days. always rounding down means you are 14 either way. This is your minimum age because 12 years 0 days is your sister's minimum age. [emoji106]

But sis also has 364 days more before her next birthday. So depending when asked she could be up to 12 years 364 days, and the maximum you could be is 2 years 182 days older.

12 years 364 days + 2 years 182 days = 14 years 546 days = 15 years 181 days. Always rounding down means 15 years old is your maximum age.

QED

Well that pretty much poisons the well for every other claim you make.

This signature is intended to irradiate people.

 

[Brainster]

As best as I can tell, the correct answer lies somewhere between 13 years and 1 day and 15 years and 363 days (ignoring leap days).

When I was 4 years old, my sister was half my age.

I could have been anywhere between 4 years old precisely (my birthday) and 4 years and 364 days, while my sister could also have been anywhere from 2 years old precisely to 2 years and 364 days. Thus, I am anywhere from 1 year and 1 day to 2 years and 364 days older than she.

Now my sister is 12 years old. How old am I?

Again, my sister is anywhere from 12 years old precisely to 12 years and 364 days. So the bottom end of the range for my age is 13 years and 1 day, and the top end is 15 years and 363 days.

 

[DevilsAdvocate]

That is correct for the "alternate" interpretation, but the max can be 363 or 364 when leap year is considered.

 

[Aepervius]

There is only one problem with your gotcha. But the udnerlying assumption of those math question , is always that the math falls on integer values of year. That is why nobody go for the assumption that it was 4 year and 364 days, because they think the puzzler does not go for a cheap gotcha, going against the basic assumptions.

In fact, nobody I know would say the boy would be 4 year old at 4+364. You would say he is ABOUT 5. You would never say he is 4 in normal conversation. That is why it is a cheap gotcha. Go ahead ask a person which is a few day or even week before anybirthday, how old they are. Most will answer "about" year +1 , with their birthday coming soon.


So yeah the answer get 3 thumb down, and one ruined birthday cake.

 

[Red Baron Farms]

Hold up.

You were born midnight 1/1/1980. At midnight 1/1/1984 you turn 4. That's 1461 days old. She's half as much at 730.5 days. So she was born noon 12/31/1981. At noon 12/31/1993, she turns 12. You are still 13 until the next day-12 hours away. On 12/31/1993 she is 12 and you are 13

incorrect. Nice try though. You sent the extra 1/2 day the wrong direction.At 12 she is 365 days x 12 = 4320 days (+3 leap days)
you will be 4320days +730.5days.(plus at least 3 and maybe 4 leap days) = squarely in the 14 th year by 1/2 a day sooner or more. You rounded that 1/2 day the wrong way. It only works to make him 13 if it is a leap day ONLY. And we already stated we wouldn't use such.

Wait, I need to recheck that second set.

check it again.

 

[jadebox]

Okay ...it is now clear that the correct answer is 14.

 

[theprestige]

incorrect. Nice try though. You sent the extra 1/2 day the wrong direction.At 12 she is 365 days x 12 = 4320 days (+3 leap days)
you will be 4320days +730.5days. = squarely in the 14 th year by 1/2 a day. You rounded that 1/2 day the wrong way. It only works to make him 13 if it is a leap day ONLY. And we already stated we wouldn't use such.

Jesus Christ. Are you still defending this turd? Your problem is stated in years. It's dishonest to change the units to days when evaluating answers.

You haven't discovered the "ultimate" anything.

You've just transformed a straightforward age calculation into an exercise in gratuitous dickery.

Edited by zooterkin: 

<SNIP>
Edited for rule 12 and rule 0.

 

[RussDill]

a person who is "4" is actually between "4" and "4 years+364 days" due to always rounding down.

So the sister will be between "2" and "2 years 182 days" younger, being half your age.

Since the definition of half your age is not stated in the problem, you cannot arbitrarily make one up and then claim to have the right answer because no one else guesses your arbitrary interpretation. A equally valid definition is that you are aged 4 years and your sister is aged 2 years, ignoring how long it is to your respective birthdays.

Your definition clearly falls flat if you compare it to how people in the real world consider one person's age to be half of another person's age. Let's not forget the rule that a court will construe ambiguous contract terms against the drafter of the agreement.

 

[DevilsAdvocate]

You would be in the 14th year (14.00821...) but you would not have reached the date of your 14th birthday, so you would still be 13 "years old" even though you have completed the 14 the trip around the sun.

Because you were born on a leap year, you lived an extra calendar day that your sister did not. When we halve your age, that puts her born an extra half day ahead. So she hits age 12 a half day sooner. Of course you are exactly the same number of days old when she turns 12 no matter when you were born. But that leap year means you have to wait another day for the calendar date of your birth date.

 

[ynot]

“When I was 4 years old” – Could mean on my 4th birthday, sometime between my 4th and 5th birthday, or I had been alive in 4 calendar years.

"my sister was half my age" – Could mean half my then age or half my current age.

"Now my sister is 12 years old" - Could mean on my sister’s 12th birthday, sometime between my sister’s 12th and 13th birthday, or my sister has been alive in 12 calendar years.

"How old am I?" - Calculate any number from the permutations above and claim it’s the “correct” answer, and that 1,755 others provided wrong and/or incomplete answers!

This thread is in the wrong section of the forum.

 

[Red Baron Farms]

Since the definition of half your age is not stated in the problem, you cannot arbitrarily make one up and then claim to have the right answer because no one else guesses your arbitrary interpretation. A equally valid definition is that you are aged 4 years and your sister is aged 2 years, ignoring how long it is to your respective birthdays.

Your definition clearly falls flat if you compare it to how people in the real world consider one person's age to be half of another person's age. Let's not forget the rule that a court will construe ambiguous contract terms against the drafter of the agreement.

I get that, which is why I have always agreed that 14 is correct, just incomplete.

It bears understanding that the problem did NOT say she was 2 though. This is the clue that signals how the puzzle is to be solved. If it had said, "When I was 4 years old, my sister was 2. Now my sister is 12 years old. How old am I?", then the answer would be either "14" or "13,14,or 15". The wording was changed to make it a puzzle. This is the type of puzzle that the smarter you are for some reason the less likely to get the right answer. We almost automatically insert 2 so strongly it is as if that is what is actually stated in the problem.So when we think deeper and consider the possibility that 4 actually is 4 + up to 364 days and 12 actually is 12 + up to 364 days, we forget that 2 is not actually stated, and we make the incorrect assumption we can state 2 + up to 364 here too.

Some will pick 24 as they double 12. Some will pick 14. Some will pick 13,14,15 not realizing, except for this falling exactly on a leap year 13 doesn't work as 1/2 was used rather than saying 2...which means it is limited to 2+ up to 182 days and the option where the sisters birthday falls prior to, allowing a 13, would mean the original criteria she would have had a chance to be 1. 1 is not half by either way of interpreting the problem so the set of options for that is thrown out. Leaving only 14 and 15, instead of 13, 14 and 15.

 

[McHrozni]

Was surfing and came across this problem:

When I was 4 years old, my sister was half my age. Now my sister is 12 years old. How old am I?


Then I got to noticing that there was a huge thread of wrong and/or incomplete answers! 1,755 answers and not a single one as far as I could find got it 100% right. Only a very few even got close. So I thought that those of you here who like math puzzles might want to try your hand at it.

Will award the complementary 3 thumbs up to the party getting it completely right, 2 thumbs for mostly right close but no cigar, 1 for correct but not complete and for using black holes and/or speed of light cheats etc et al.

Since you went as far as to break down the meaning of "X years old", you really should explain which, if any, time dilatation anomalies were present. It is entirely possible for you to be 4 years old still, any answer that doesn't encompass that is also incomplete, including your 'ultimate' answer.

McHrozni

 

[Red Baron Farms]

Since you went as far as to break down the meaning of "X years old", you really should explain which, if any, time dilatation anomalies were present. It is entirely possible for you to be 4 years old still, any answer that doesn't encompass that is also incomplete, including your 'ultimate' answer.

McHrozni

I did "Will award the complementary 3 thumbs up to the party getting it completely right, 2 thumbs for mostly right close but no cigar, 1 for correct but not complete and for using black holes and/or speed of light cheats etc et al."
post #1

 

[McHrozni]

I did "Will award the complementary 3 thumbs up to the party getting it completely right, 2 thumbs for mostly right close but no cigar, 1 for correct but not complete and for using black holes and/or speed of light cheats etc et al."
post #1

I know, I cited the post. Your supposedly "complete" answer did not include time dilatation due to effects of speed or gravity.

wait til sis becomes 12, then you are between 14 and 14 years +182 days. always rounding down means you are 14 either way. This is your minimum age because 12 years 0 days is your sister's minimum age.

http://www.internationalskeptics.com/forums/showpost.php?p=11910866&postcount=77

If we include wormholes there is no minimum or maximum age you could be. This answer is at least as reasonable as your answer to the question. At a minimum you need to add there were no time dilatation effects greater for either of you during this time.

McHrozni

 

[3point14]

Well, that's five minutes of my life I won't get back.